Erratic page: sometimes values are not displayed

Sometimes my pages don’t work correctly: They don’t show values although they’re available in the items (and color sliders are not correct either):

Available data:

And this is what it looks like sometimes:

And sometimes it doesn’t work on my mac but on my windows PC. Right now for example, it doesn’t work on my mac (chrome) but works fine on windows (chrome and firefox), but yesterday evening it didn’t work on either system. Here’s what it looks like working ) now (windows, chrome, dark mode):

That’s all the information I can give right now. I tried to find the log files, but frontail ( is empty and I don’t seem to have a directory for log files (using hassle-free installation on Raspi); there is no “openhab”-directory in /var/log. Maybe you have an explanation/solution anyway?