MIRO - Double FI document

Dear Gurus,

i'm trying to release an invoice through MIRO.

The posting date is 31.12.2015, when i save the system says that last document posted has date 10.01.2016.

Since this validation exit shouldn't run, i activated the trace of validation, and i noticed that when i run MIRO there is a double run of validations, one with BUDAT 31.12.2015, and after this another with budat 01.01.2016.

It's like the MIRO is generating 2 invoices!

I noticed that i'm experiencing this problem when there are Material account position (i saw it by simulating).

Is there a note or something else that can solve this double invoice problem?

thanks

Gianni