This has been an issue for me ever since owning an s9.
The buttons are impossible to press with a screen protector on. I have to remove the protector type my password then re-apply screen protector. Samsung only alows sensitvity settings once the phone boots which is annoying
I haven't seen this type of error reports from other Beta users yet. Please report this problem through Beta Feedback in Samsung Members right after the issue occurs. Hope that the developers will find the cause of it quickly!
My suggestion (might sound silly) is to disable password, pin, fingerprint etc when using beta ROM. Its BETA, in worst scenario you might be unable to enter unlock pass or pin at all. As a precaution disabling pin, pass etc for the time you're using beta might smooth things a bit.