Since the system was recently serviced it might be worth having the tech come out again/further service, it might have been that the heatsinks were not setup properly etc. or maybe are loose (this typicallly never happens but it could be something random). When it does get this hot if you go to Task Manager does it show anything eating up CPU % besides what's supposed to be?
the CPU load values don't go usually beyond 25-40%
i have felt that playing Youtube has an effect on temps, both CPU and GPU (doesn't have discrete graphics) of about 5-7C. (goes from 43C to 50-51C when youtube is playing a video)
the keyboard is not getting hot but it's very noticeable and warm enough to be felt
I think you are right either it's problem of fit or something random