Do Check by Signing out from the Server and whether the Robot logs in to the Server and Performs the operations correctly.
We could then narrow down the problem to the Minimize Screen/Locked Screen that is being checked.
Also, Some Posts which may be useful regarding process run on minimisation of windows :
Yoichi
Gautham_Pattabiraman
Anil_G
lrtetala
ashokkarale
Angel_Meseguer_piqueras
FINNNNNNNN
kardelencihangir
ayumi.ouchi
Gabriele_Radici