When I tried to reduce to a small block of code the problems disappeared so it was not an example.

That's precisely the point. If you cannot provide an SSCCE because the problem disappears then the problem is with your code and not with anything else.

Your code is somehow (perhaps indirectly) calling DBI->connect without a proper DSN. That is the issue - it's up to you to find out where in your code this is occuring and fix it there.