Bug Description

After switching to Hermes I noticed an unusual behavior. Every couple of minutes my RN app stops responding to user interactions, more specifically the JS thread freezes for a couple of seconds. Meanwhile everything than runs natively on Android side (scrolling, typing text, etc.) works just fine, only JS is blocked from execution. After 5-20 seconds it "unfreezes" and all the code that was supposed to be run while the app was unresponsive (while the user was tapping different things) executes immediately. Then everything goes back to normal until the next freeze.

This stops reproducing after switching from Hermes to JSC.
Also I've noticed that using the version that supports Proxy (0.4.2-rc1, which I need because the app uses MobX 5) makes the freezes occur more frequently.

What I observed so far is:

• The problem is not affected by dev mode (persists in release builds)
• It is not specific to my device (reproduced on both Samsung device running Android 10 and Xiaomi device running Android 7.1.2)

I don't know at all how to debug this issue or how to narrow it down. It doesn't seem to be caused by any specific user behavior inside the app - it's usually enough to just launch the app and keep it open for a couple of minutes.
There are no errors, no crashes, nothing in Logcat, etc. The app just stops responding and then goes back to normal.

That said, I cannot provide any reproducible demo, but I am willing to help finding the issue. I just need help with finding what causes it. Maybe there is some debug info from Hermes internal that I can collect?
What also makes it harder to narrow it down is that the app I'm working on is relatively big (over 20 000 lines of own code and a lot of dependencies).

Hermes version: 0.3.0, 0.4.1, 0.4.2-rc1
React Native version (if any): 0.62.2
Android version (if any): 10.0, 7.1.2
Platform (most likely one of arm64-v8a, armeabi-v7a, x86, x86_64): arm64-v8a