In MP execute on the client:
player removeallmpeventhandlers "mprespawn";
player addmpeventhandler ["mprespawn", {diag_log ["mprespawnCLIENT", _this]}];
throw 2 grenades under yourself -> event registers in client .rpt not server
execute on the server:
(playableUnits select 0) removeallmpeventhandlers "mprespawn";
(playableUnits select 0) addmpeventhandler ["mprespawn", {diag_log ["mprespawnSERVER", _this]}];
again it registers on the client only.