[Bug] ProtonMail Keeps Getting Logged Out

Good day/night, and thank you very much for Native Alpha, which is (mostly) working great for me as a lightweight isolating solution for certain online services (Amazon US/DE/FR, etc., and AliExpress, as well as ProtonMail).

Unfortunately, I keep getting logged out from ProtonMail at irregular intervals, something that not happening to me with any other service.

Also, and this does affect all services, but cleaning the cache with SD Maid also clears cookies for all services.

System Specifications
Device: Razer Phone 2
OS: Stock Android 9 (roughly the same as AOSP), mostly deGoogled (had issues flashing custom ROMs, and USB port gave out before I had time to properly diagnose the issue)
WebView: Google 138.0.7204.181