André P.

This is fixed for v3.5. See CORE-1718 for a comment on the task that describes how to resolve it in the meantime.

I wonder if that was me via ticket system. :-D
 
I reported this, too. But for v3.4.4.
 
The credit of the client was 203,63€. It is configured to auto-use loose credit, but it didn't. (cronjob run fine).
In the client interface I tried to do the same thing you just described. It said something like "Select a payment method" etc.
 
Next step I did was using the admin interface to apply the clients credit, which did not work.
I also tried to record a payment of the total due, which was 12,50€. I recorded 12,50 and got an error1. I recorded 14 and it worked. 
 
Very strange
 
I hope it is okay to post here though I opened a ticket. Paul does a great job helping me @support. :-)
Just want to share my findings.
 
1 Error: "One or more Amount to Pay values could not be applied to the specified invoice. Ensure that the Amount to Pay does not exceed the Amount Due on the invoice, that the invoice is open, and the sum of the Amount to Pay values do not exceed the Payment or Credit Amount."
 
Excuse my English, I am not a native speaker. If I can provide you with further information, let me know.

I already collected a great rule set, but am still pretty far away from complete.
It runs great so far.