Clevo P750ZM+Win 10+5.1 Analogue=No sound fronts/HPs!

I'm at my wit's end here so help is much appreciated. Spent ages fiddling with drivers and cables and still the same problem.

I'm using Logitech Z-5500 5.1 Analogue cables (Green, Yellow and Black) for surround sound output. Worked perfectly on tmy AW 17 on Win 7 so nothing's wrong with the speakers or cables. The P750ZM came blank and I installed Win 10 fresh (the latest mainstream built, not preview) 5.1 Analogue has been hit and miss (now only miss!)

The 3 drivers I've tried so far for the Realtek ACL892 onboard soundcard (all clean installs) were: Clevo site (old version), Realtek site (R2.79), and Windows Update-exclusive (latest). All three resulted in this specific problem: no sound at all from the front speakers/headphones jack (immediately next to S/PDIF jack) connected to the Green Cable (also tested with iPhone headset and no sound either). Sound came out perfectly from the next 2 jacks, which were tasked as Centre/Sub out (Yellow) and Side speakers out (Black). Also when ONLY the Green cable is plugged in there was a very strong static signal from the speakers, which disappeared once the other 2 cables were plugged in.

One thing I noticed in Realtek HD Audio Manager was that the Front/HPs jack (for Green) did not have Connector Retasking enabled, nor pop up dialogues to select output, unlike the other 2 jacks. Probably because those 2 shared the same input with Mic-in (Yellow) and Line-in (Black).

Months ago after ages of meddling with cables, re-nstalling drivers, reassigning jacks in RegEdit somehow I (briefly) managed to make things work with surround sound coming out of all speakers. Thinking it might be how Realtek drivers controlled the jacks I saved a backup copy of the binary entries,which came out like this:

Pin12 01 00 00 00
Pin18 06 00 00 00
Pin1a 07 00 00 00
Pin1b 02 00 00 00

So switched off my Clevo. Forgot about it for a few months (yeah the AW 17 kept me busy ;p), now turned it back on (and faced the barrage of Windows Update), and yet again, no sound from fronts/HPs despite nothing had changed since I last touched it. I dreaded the thought of something hardware-related in that cursed jack . Did Windows 10 and whatever 'updates' MS keep churning out break my system?