Hi, @Oliver2.
I’ve had a similar problem with my iPhone 6s. I always thought it happened because my phone is always running out of free space. Very frequently I need to restart it for it to release some space, but now that I read this thread I started suspecting of the progressive web app.
I also added a PWA and many times it gets temporarily frozen when I switch to other apps or the screen is turned off. I don’t leave it on all the time and don’t use it only to access OpenHAB (MainUI).
I think it happened even when I was running OpenHAB 2.5 on a RPi 3B (OpenHABian and the supported JDK). I updated OpenHAB to 3.0 and 3.1 on the same RPi and kept having the same problem.
I replaced the RPi for an RPi 4B (CentOS 64-bits + OpenJDK 11 64-bits) and keep having the same problem.
Going back to the PWA, sometimes when I reopen it, I have to wait a little bit for it to become responsive and load another page for it to work again. Sometimes it doesn’t become responsive and I have to close the app and open it again. I never close apps unless they behave strange.
When I load the MainUI directly on Safari I don’t have those problems.