If you are generating app access tokens/server to server tokens.
This may suggest you have a rogue job that is generating a new token every time instead of reusing a token. And you his the max token count.
If you generate 50 (valid) tokens
When you generate token 51, it force kills token 1.
So it sounds like you have a rogue job that is not reusing a token.
And the good job is getting a dead token as a result.
You could use the validate endpoint but the validate endpoint would just give you the same error, the token is dead.