Time Capsule stopped backing up a few months ago

If the Back Up With Consistency Scan fails, then the backup file of the MacBook is likely corrupted. You can delete/erase only the backup for the MacBook and leave the other backups of other Macs intact on the Time Capsule......so you won't have to erase the entire Time Capsule disk and lose all the other backups of the other Macs.

Your first post did not mention that other Macs were also backing up to the Time Capsule, so we assumed that the MacBook was the only Mac backing up.

As far as your Time Capsule, it is at least 7 years old and possibly even much older depending on when the Time Capsule was originally placed into service. 5 years is about it as far as the average useful life of the Time Capsule, so you have had very good luck with the product. But, it's time to start thinking about another plan to back up your Macs.

It's your call, but I would not keep any data that I could not afford to lose on the Time Capsule since the power supply and hard drive are frankly both overdue to fail at this point.

What operating system is installed on the MacBook? We ask because countless numbers of users......including me......have had problems with Time Machine backups after "upgrading" to Catalina 10.15.x, so that might be one possibility for the issue. In my case, I did have to erase the Time Capsule hard drive and start over again with a new backup. Unfortunately, the backup became corrupted after about 6 weeks or so, and I had to start all over again.

About how old is the Time Capsule? If there is an error on the Time Capsule disk, that too will prevent a backup from running successfully. If the Time Capsule is 5+ years old, then the product is "suspect".

As is stands now, you have done about all that you can do, so if you want to try to continue using the Time Capsule, it would be worth a try to erase the drive and start over again to see if this will help. Please understand that there are no guarantees here that things will straighten out.

Before you erase the drive, I would try a backup one more time as follows:

Hold down the Shift key on the Mac while you click on the Time Machine "clock" icon at the top of the Mac's screen

Select Back Up With Consistency Scan

If the backup still fails, it's time to try erasing the drive unless the Time Capsule is an older product, in which case it is likely starting to head downhill. Any of the older "flat" or "square" Time Capsules that look like a small white pizza box would fall into this category.

Good plan!