It’s hard to tell based on your description. The gibberish error messages could’ve indicated the cause, you probably still can find them in the older log files.
This seems to be the biggest mystery to me. The only thing that I can think of in this context, is that “something happened” with the vault’s location. Is it located in some cloud storage? Did it need some time to synchronize?
But depending on the error messages, the cloud storage could be unrelated and you experienced a different (temporary) issue.