To everyone having the same problem. I would like to tell you that this solution worked for me (though I am not sure if it will be for the long term).
My problem is the same as the one in the description. I also use an external monitor and my internal display of my laptop is 300hz. I afk'ed for 1 hour and came back at my external monitor not picking up any source + my laptop display monitor became so bad and upon inspection it was capped at 66hz.
After further research and a few reddit posts, it seems that Windows Update is the culprit behind all this. Unknowingly, I had 2 version of AMD Adrenalin in the AMD folder.
What I did:
- Disabled Windows Updates to update graphics driver (from a separate reddit post)
- Followed this solution.
After uninstalling, and restarting. I can finally see that it was not the case anymore. I can set my refresh rate back to 300hz. The display monitor is now connected to another amd driver. I reinstalled latest AMD Adrenalin and now it works.