HTC Vive: trigger or grip button keeps being pressed

I used to use the following two lines in Update() to find out if the user has pressed the trigger:

Most of the time this works pretty well, but sometimes the button seems to be stuck: after releasing the trigger or grip, device.GetPressUp stays false in every frame (even calling this in FixedUpdate didn't help).

So I changed my code to only use this:...

HTC Vive: trigger or grip button keeps being pressed