Question Laptop performance drops when charger is plugged in, but it works fine on just battery power ?

[puuhuu]

Laptop model: HP Pavilion Gaming - 15-dk0056wm.

The FPS drops to around 5-40 FPS when I plug in the charger but on battery alone I get 140-200 FPS.
I've had this laptop for years and it worked fine, didn't have the problem when I got it, in fact it boosted performance with charger plugged in. Before I used a different charger and some games got perfect fps on that charger, others not so much, I no longer have this luck.

When I restart the laptop with the charger plugged in and it gets maybe 46 fps at most, unplug it and plug it back in again, FPS drops to about 5-30, average 20.

This is what I have tried:

• bought a new charger
• replaced charging port
• tried different charger
• update bios
• changed bios settings
• changed nvidia control panel settings
• changed graphics settings
• updated nvidia drivers / removed them
• changed power plan, max/min processor and graphics performance settings
• changed outlet

The only thing I haven't done is applied new thermal paste. I've had it for almost 4 years and rarely used it, mostly for gaming every so often. It needs a screen replacement, works fine . If all else fails, I'm just going to sell it really cheap on ebay, I already have it listed, it's doing my head in.

here are the specs:

Intel Core i5 9300h

Nvidia gtx 1650

8gb Ram ddr4 2666 (i dont know the brand)

256gb SSD

Windows 11