Game stuttering only in iPhoneX and above. Not a performance issue.

Unity Version: 2017.4 (LTS), 2018 and 2019.

Every project we have published has the same issue and always only on iPhone XR/XS and above. The game seems to stutter / microfreeze regularly with no apparent reason.

The profiler (Connecting the devices to the editor) shows nothing on those bad spikes.

There're not Physics or Camera track issues because we've resolved every related issue and every game works smoothly fine in iPhone 5, 6, 7 and 8.

Any suggestions? We've run out of ideas already.

Thanks!