I have this exact problem down to the core. I have tried everything I can think of. My TX PCB replacement flashed to v1.91 correctly, but now that I want to update to v1.92 I can't get into vendor mode.
I followed the guide to get to v1.91, but now all I am trying to do is intro and I can't get past it. I tried on all sorts of chipsets that have always worked in the past, and now that I am on the PCB Replacement with 0272 v1.91, I can't get into vendor mode on anything.
I have tried DosFlash v1.8/1.9/2.0 on several chipsets, including one with IDE mode set on a SATA2 Controller. None of them worked.
You can see what I mean by looking at my post here:
http://team-xecuter.com/forums/showthread.php?t=63538&page=7
Everyone keeps regurgitating the same answer: BUY AN X360USB PRO, but I can't, they are out of stock. Plus even if I could, why give up on hardware that has always worked in the past? Clearly something else seems amiss.
EDIT: I have tried different versions of JF, v1.66, v1.85, v1.86, and v1.87. I have tried Slim Key, and Slim UnLock. Can't get into vendor mode.
Hardware: CK3 Lite, TX PCB Replacement, and the chipsets listed in the other post.
*Note: ~Craig~ and I have the same recommended VIA card. Both same problem. I believe their are 6+ different SATA connections being tried here, and yet we all have problems... They all used to work. So what the hell is making the PCB not go into vendor mode.