O2 sensor, possibly dead?

[shinobiu]

Hello all, long time lurker, first time poster. I was hunting some misfiring and high STFTproblrms on my 2.5t, which turned out to be melted tip on nr.3 spark plug(with only 3K km on it), and after afresh set of plugs things got better, but I still had fluctuations in fuel trim (it would go from 6% in the morning to -6 in the afternoon, with STFT going all the way to 25% at idle). Google has led me to possible O2 sensor or catalyst problem. I fired up Vida and noticed that my upstream sensor stays flatline, while downstream makes a wawe pattern(as far as I found online it should be opposite). I have added schreenshots of graphs of a short ride to give you a example. Car has new PCV, new coils,new plugs, service. It has LPG installed, but readings are the same no matter which fuel I use. Any help would be greatly appreciated