When the new day runs for Towny it appears that upkeep is not withdrawn from the towns at all. I'm running the newest versions of Towny, Vault, and Gringotts. The towns are using town vaults exclusively.

This is actually the same issue I posted. Its a concurrent modification error.

Issue #88

Closing as duplicate then.

If you really are on the newest version of towny. I have added a setting value for async economy timers

Please set that value to false to fix this issue. It is basically a work around until this plugin is thread safe.

  use_async: 'true'

Should be set to

  use_async: 'false'