TC reported A side cab door opened by itself. TC closed back - ok. ~~~~~ 3622 - TC reported A side cab door opened by it self.  EMU 3622 A side cab door handle/budget key after twisting to open, unable to spring back. Once cab door was closed, the handle was still stuck in an open postition, thus re-opening the cab door. Serviced the stiff latch and mechanism; movement became much smoother. Function tested 20x, cab door handle was able to spring back. Door did not open by itself any more. Done by: Yusof 45260