Issue with extended rebate settlement

Hi there

i am using Extended rebate processing and try to work out a scenario where there are three invoices with materials A, B, C and i try to create a settlement credit memo on these materials (not the Settlement material). The infostructure S469 gets updated ok.

when i run the settlement on the agreement with RBT_ENH_VB7 i get the error on the agreement "document is blocked for billing". I can even release the agreement with VKM3 but nothing changes.

I am absolutely clueless what this message means as there should be no billing block on the agreement? Per customizing there should also be no directly blocked credit memo request but regardless: i cant even create a settlement document...

Thanks for your help

Kai