iPhone xs max taptic engine

[Jomppa]

My xs max taptic engine started acting up 2 days ago. Worked flawless in the morning and by end of day it first stopped working which was fixed by reboot. By the time i went to sleep and put it on the charger it made the rattle noise from taptic engine. Next day i rebooted it and it worked flawless for about 2 hours and then stopped again, reboot and rattle noise, reboot and working like supposed for a few mins, reboot and rattle, reboot and again working like supposed. I reinstalled 12.1 today and worked like a charm for an hour and suddenly rattle again. Has not been dropped or bumped into anything. I have a apple silicone case on. The thing that baffles me is that it works like supposed every 2-3 reboot and after awhile laying on table it either rattle or dont work at all, then with enough reboots it works properly. Hardware or software problem? I had the 6s with taptic engine rattle but that phone never stopped the rattle once it begun so it was a straight hw problem. Now with the xs max it works 1/3 reboots as it should and rest of time either rattle or dont work at all.