PE errors when entering in UNITS with a PE of "U"

Hello,

I am trying to use P510212 (progress entries by job ) to enter in actual production units into a cost account.

The cost code/cost type structure is as follows:

48802.0997.510212   PE of "U"

I can enter in units via a regular JE, but when I try to enter in actual units via P510212 (Progress entry by job) I get PE errors.

Any ideas on why the P510212 would be giving me errors?

Thanks