I have a story that I believe its knox related.
Couple of months ago I broke the screen of my first i9192 knox free phone, then I bought the second one wich came with knox bootloader.
I didnt mod my 2nd. phone because i didn't whant to trip knox and loose warranty, just rooted with saferoot it worked flawlesly all the time in 3g/2g auto, i never got any problems.
By the time cm11 came out i was so happy that i din't care about warranty and triped knox installing latest cwm recovery, flashed cm11 and it worked fine but I had a lot of signal drops while using 3G, but still I move on in 2g mode only I tried every build but still I have signal drops while using 3g mode some times where better than others, but still after some time the phone lost 3g signal, then I get bad quality on calls not connected to the network and no signal at all, but at the time I choose GSM only mode the signal got back and working fine but only in GSM mode, but none of the users of cm11 reported my issue then i thought was my modem tried different ones but with all i got bad quality on calls and network drops if i select 3G mode, even "wcdma auto" or "wcdma only" i end with no signal, no network, bad quality on calls that was fixed using "GMS only"
yesterday I was sugested to try back a stock firmware, the latest blackedition i proceed with the instalation, but my sorprise was that the issue persist, network drops in 3G mode bad quality of calls and not registered on network, then tried my phone with different simcards and all seems to work in 3g but didn't have the time to try them for long time, then its like mine that works for some time then drops, but my simcards were working flawles and connecting 3g signal on other phones then I didn't blame the sims, since they work on other phones.
still sad and pissed off I came home and disassembly the phone and exchange mainboards. the phone booted normaly in the old rom and working fine and connecting to 3G, then I update recovery and install a cm11 to test.
From yesterday untill now my phone has been working flawlesly on cm11 with the old knox free board, then I blame tripping Knox all the problems I had with 3G signal and somehow screwing the modem.
This video is with the Knox 0x1 board and the "bug"
This video is with the Knox free bootloader board, wcdma works in both sims.