I have lots of issues with tvheadend 4.3 if it comes to german HD television. To be honest - it is a totally unusable version. I’m running on Intel platform with a Dell 7060 computer that has really more than enough power.
The developers of tvheadend complained that the version i’m using is higly outdated. Is there a chance that you provide the latest version 4.3 build for download in libreelec?
If the latest 4.3 version - that should be a final for about more than a year has no fix I would reinstall with a 4.2 that was at least running for nearby 15 years on an athlon - stable… the worse my super slow athlon gone broken ☹️