I had this issue a couple months back and had decided to follow this thread. I got my phone fixed a few days after I noticed the issue.
The issue was that a small component holding the Taptic Engine in place was loose and out of place. It was a simple fix, but compromised the phone’s water resistance. This is because Apple service centers in my country don’t fix these issues, so I had to go to a third party repair store (where obviously, replacing water resistance seals isn’t available). If you live in a country where official Apple stores exist, you should get your phone fixed there. Either way, it was a simple and rather inexpensive fix.