Frame loss contrary to performance graph indication

[NonsoluteAbsense]

Whenever I try to play a game, I keep randomly losing frames despite all in-game performance graphs showing very consistent performance/FPS.
 

I've tested it with different monitor/cable combinations (both DisplayPort and HDMI), but the issue sustains, so I've ruled out a Monitor Hardware issue.
 

CPU (AMD Ryzen 5 5600G) and GPU (NVIDIA GeForce GTX 1660 Super) temps all stay consistent, around 50C and 55C respectively.
 

I feel like it's probably one of those super simple fixes that somehow never crossed my mind so any suggestions, no matter how small, would be appreciated.

[manikyath]

if everything shows consistent performance, how are you determining these "lost frames"?

[NonsoluteAbsense]

36 minutes ago, manikyath said:

if everything shows consistent performance, how are you determining these "lost frames"?

In the in-game performance graphs, it shows consistent 165fps (this is just the prime example I'm using, but it happens at all refresh rates/fps caps I've tried), but I can see the frame rate visibly drop as it's quite noticeable. However, I've ruled out monitor refresh issues since I've used several combinations of monitors/cables and the problem persists, so I'm assuming it must be a GPU-related issue. I took the GPU out yesterday and did some light cleaning, but I'm wondering if a deeper clean is required.