Memory leaks on Python 3.14

Our memory checker wasn't working properly. Now that it is fixed, !968 (merged), we see many leaks. We should fix these before our 10.3.0 release.

E.g., https://gitlab.com/tango-controls/pytango/-/jobs/12997497595

Update: after testing on various Python versions, we only see the leaks on Python 3.14.