I think I'm a little closer to figuring this out but am still stuck. We do have an enhancement that is being invoked with screen variant '1' on LM00 logon. If I don't invoke the enhanced screen, the Enter button on RF gun works correctly. This is with standard SAPPLLMOB, screen 2052.
With enhancement, what I see is SAPLLMOB calling screen 1502. And program (subscreen) SAPLXLRF calling screen 9052.
In config V_T3130F, I've tried entry for SAPLLMOB/1502 and SAPLXLRF/9052. Neither works. Only thing I haven't tried is both entries at same time. Obviously I'm starting to fish here and may need to involve a developer for help.