I've not seen a seed format like this before and before now, I almost wouldn't believe seeds request itself in concession, you're lucky your hard drive is still intact, it could've been worse.
Hope you removed and kept your hard drive before taking it for repairs? If you didn't I recommend you create a new wallet in another device and transfer out the funds, then reinstall the OS of the computer. You never can tell what was introduced into the PC at the point of repair.

Nope, I learned from the onset that you can't call something a backup until verified. Before I store a backup, I always import another instance of the wallet in the same device, place the two windows side by side and compare the addresses, if it matches, then the seeds are correct.

I didn't make this mistake, but I did forget to keep the seed when I first started out. Because I started out way before any of these seed things were common, so my very first ever electrum, I forgot to take it.

I was lucky enough that it didn't had much money in it, even after so many years, it is still like seven dollars in it or something last I checked, probably much lower now that the price went down so lot. But if I had any decent money in it, I would not have any way to get in and that would be terrible.

Omitting a word from your seed phrase is a very costly mistake and this can make you lose all your bitcoin, I have not made such mistake before because I always review my seed phrase before storing them in a safe place. I will repeatedly read what I wrote down so as not to make mistake, i also take note of every word so I do not spell them wrongly, this is also a mistake people make as they spell the words wrong instead of copying exactly what is written as their seed phrase. There is no way to recover from this hence it is a mistake I will not want to happen to me and as such I will always do everything possible not to experience this and hope that I really do not experience it.

Such mistakes can be avoided and that's why when writing down your seedphrase you should do it with due diligence. Or better still, as someone smart, have more than one back up of your seedphrase written down and stored in different locations. In the case of op, it wouldn't even have been a problem if he did have different backups written down. He simply would have gone straight to find the second backup and use it to access his funds. We all know that the worst part in our crypto journey is losing access to your funds and no one wants that. That's why you have to do anything that concerns your keys without making mistakes. Even if there are few ways to recovering your seedphrase, the chances are normally slim, so it's better to be careful..

Of course, Bitcoin will last forever, and it will be timeless. It will disappear if it can no longer be trusted, but is there a scenario where that could happen ? I don't think so, because Bitcoin has proven itself to be resilient to any issue; that has been raised against it. In fact, you can now see that many institutions are involved in Bitcoin, either directly or indirectly.

Regarding lost private keys or seedphrases, the Bitcoin contained within them will be lost forever (as long as they can no longer be accessed or there is no way to find them). Therefore, keep your personal data (including data related to your personal wallet) well, neatly, and securely. Personally, I have backed up my crypto wallet, and if I were to die today, I would have prepared it for my family. So, if you don't want your Bitcoin to simply disappear, consider storing it securely, and share it with someone you trust (but, I suggest don't let them access it, while you are still alive). Cmiiw.

By the way, as far as I know, the problem you are experiencing can still be resolved by using the brute-force method. This involves trying several possibilities for the missing words, but not all of them, just a few (if I am not mistaken, around 1-3 words). The fewer words missing (for example, just one word), then the faster the recovery process will be - compared to 2 or 3 missing words. I have seen several posts explaining how to do this, and you can see one of them here : The FinderOuter, a bitcoin recovery tool - by @Coding Enthusiast

or, you can also see the following : btcrecover.readthedocs.io ( Keep DYOR )

Btw again, I suggest you not to give out words from your seedphrase, especially if there is Bitcoin in it, it is very dangerous, you know.

So you had a valid wrong seed ?

Always reimport your seed.. I don’t know how coinom handle this aspect but even if you have a wrong valid seed , the moment  you reimport it.. it becomes your new seed without needing to worry about losing anything. Unless the error gave you an invalid seed which you will eventually catch and generate a new seed or check the old if it’s still available.. problem solved!Clipboard is accessible before .. OP could have copied , input the copied words singly since clipboard is not accessible this time , happy to have a working wallet, forget to save it as a file , shutdown or close application holding the unsaved details, seed lost forever.

What an annoying mistakes. Though I haven't experienced this kind of mistake while storing mine, because I was actually careful enough from the starting. I do verified every single words in the seedphrase before saving or writing it down for future use. I actually kept my copies in a place I know I won't forget or lose easily. Including records book,the family photos/album and at the back of my school certificate and I also stored it in my device. I did that because I knew the device am using could just fail unexpectedly due to over heating and even if i misplaced one, i cannot misplace others.  So the best way to protect our seed phrase is to make sure you have double check every single words you see, and don't just relay on saving it on device alone, store them offline and make sure it works when tested before trusting it, to avoid stories that touches the heart.

I his mistake as annoying one too that I don't think it's a mistake, it's negligence that he didn't pay attention to where he want to keep his money. Seed phrase are sensitive, if you must do a back up, you have to be very careful of how you copy it because one mistake in a letter, it will not be recognized. He is lucky it was not private key he made this mistake, it would have been hard to recover characters from a private key.

To create a crypto code we use 12 to 24 random words these are called seed phrase  These are used in your crypto as a master key . If your mobile or computer is dead and out of order so you can open your ID by using seed phrase in any other computer or mobile . Many people save this seed phrase in their google backup or many people took their screen shot which is not a save way .If your mobile or Gmail is hack so with your seed phrase there is always a risk of losing your money and data so we should write them in our register or copy to save them .