Hi @dk1978,
indeed, the Fairphone logo was persisting, it turned out to be recovery mode.
Both slots had an usuccessful state, that was probably the main cause.
I was able to fix that and finally boot the image that I compiled on Tuesday.
Very cool, the GSM modem works now and LTE is also there 
So far, I do not have TWRP installed, so the recovery mode was using my kernel, booted half and just displayed the Fairphone logo (I do not know if this is normal or not).
It took a while to find out what was going on (in the end adb get-state also said “recovery”).
After flashing vbmeta with --disable-verification I ran into the same problems as k4y0z here:
So I had to disable it again (and care about the slot success states).
Does it work for you?