Questions about how the taptic engine works (rattling & not working)

I've been doing quite a lot of repairs on my phone, including replacing the battery and lightning port assembly. After the last repair my phone made a weird rattling noise and felt strange when vibrating (but not when the home button was "pressed"). After some troubleshooting I replaced the taptic engine. With the replacement part the phone does not vibrate at all, only when pressing the home button. I put back the original taptic engine and I had the rattling vibration again, but this time also when pressing the home button. Again putting back the new taptic engine the home button works perfectly but no other vibrations.

So my questions are the following:

1. Does the taptic engine also make the haptic feedback for the home button? It seems like the haptic works independently from the vibration a lot of the time.
2. Could this be a software issue? I've have disabled vibrations for a while now when using the phone with the original faulty part, is it possible it has gotten stuck in this mode? I've tried force restarting the phone.
3. Is the iPhone SE 2020 and the iPhone 8 taptic engines compatible. The replacement part I bought was sold as compatible for both models, but I know from experience that this isn't the case with e.g. the lightning connector assembly or battery.