Just want to join in to report that Disable the lcd4linux has helped me in my "tune failed" problem (sometimes when zapping signal showing 0% and getting a "tune failed" and then tuned OK) on my VU+ Ultimo 4K
Problem has been there on openpli 6.1, 6.2 and 7.0 but not on the "factory" VU+ image. first i tried to change the Diseqc and bought a Spaun, did not help.
I have 2 S2 fbc tuners and one non fbc DVB-C tuner and the "tune failed" problem has only been seen on the fbc tuners.
This input will probably not help in finding where the problem is but i just want to write that it helped me also on the Ultimo 4K box.