This is very similar to an issue posted on April 13th. I first noticed this a few days ago, but it's also shows up on my first modded KSP v 1.12.3 too. For me the throttle and acceleration values are linked in ascent guidance and, of course, utilities. When one is changed the other changes along with it. One thing I did check is that the problem pops up immediately in a new install of v1.12.3 that's CKAN modded with only MJ2 and its Module Manager dependency. The new test install is a downloaded beta from Steam, verified, and then copied to a new folder for testing. I'm going to try downloading MJ2 and manually installing it. I use CKAN for virtually all mod installs.

The new Perfect Division launcher was not included in the new test install of KSP v1.12.3 and launches from the normal KSP_x64 .exe launcher. (EDIT: Turns out it is now automatically installed by Steam even on the older "beta" version of Steam KSP v1.12.3. I deleted the "PD Launcher" folder and launch from KSP_x64.exe.)

This issue puts a BIG STOP for enjoying KSP and any help would be greatly appreciated.

EDIT: Here's a link to my latest KSP Player.log -> https://drive.google.com/drive/folders/19Ndy7NfR-3NoiPcGfV509SJDvczjXXDO?usp=sharing

I also tried the manual installation of MJ2 and MM and the throttle and acceleration are still linked and changing together. I'm very much at a loss here.