Refresh rate defaulting to 75Hz (sometimes) on LG HDR WQHD+ monitor

Hi, I have a MacBook Pro 16inch 2021, M1 Max chip, 64 GB running Sequoia on LG HDR WQHD + monitor. I run parallels (all up to date) for CAD software (have done for over a decade) and for some reason, the refresh rate sometimes defaults to 75Hz if the machine is left in sleep mode, especially after a weekend. When trying to change back to the 144Hz, the only options are 75Hz or 60Hz - which does not display CAD correctly. The only way in which I can resolve the issue is to completely re-start the machine which just becomes irritating when you want to pick up from where you left from. Have read many threads on this but nothing specific to this issue. Is there anyone experiencing the same problem? Thanks - Pete