FV50 - Parking not possible during batch input

Dear SDN,

our client has a custom program for GL Document batch input through TCode FV50.

Though the answer should not be, the question here is very straightforward: why, in this program, the mentioned error occurs for some users, but not for others, giving ALL the input parameters are the same???

1 - Batch input runs

2 - FV50 is displayed

3 - (Menu) Document -> Park

4 - Error: FP140 - Msg: "Parking not possible during batch input"

Note: User who gets the error has ALL the authorizations that users who don't get the error have.

Any suggestion is highly appreciated.

Regards,

Fabio