Batch Data Entry payment_instrument is now required?
We had one client inform us that they could not save Batch Data - everything we tried to replicate the issue failed. In the end we concluded that it was due to browser caching which the client was able to confirm by testing with a different browser.

Refreshing the chrome caching (https://support.google.com/accounts/answer/32050?co=GENIE.Platform%3DDesktop&amp;hl=en) sorted it for them.

May not relate to your situation at all.