XPS 15 9500, CPU clock speed does not go down

<Different model, new thread. DELL-Admin>

Hi, Im having the same problem with my xps 9500, CPU doesnt downclock when its idleing, cpu usage will be below 12% and clock are almost always above 4.2ghz. When I unplug it for the charger it does get better, it downclocks even bellow 1.2ghz. I did check the solution you mentioned, but it doesnt seem to fix it for me. Ive setted AC values to be like the DC values, restarted laptop. but it didnt fix it. it still worse when its pluged in. Is there any other thing I can try to fix it?