AR invoices transaction number is not incrementing/duplicating

Summary:

When creating/loading invoice via excel template, system allows duplicate transaction number - does not create a unique/incrementing transaction number.

This only happens for some transaction types.

Allow duplicate transaction numbers in Manage Transaction Sources is unchecked.

What else or where else should we check?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

25a

Code Snippet (add any code snippets that support your topic, if applicable):