Flickering images on certain games (such as Battletoads snakes)

[Rageypoo]

Describe the bug I've noticed certain games present a strange flickering that doesn't exist on original hardware. This flickering happens across multiple platforms such as GG and Colecovision but I've noticed it most on Battletoads for Sega Genesis. This flickering DOES happen on LCD screens as well so the DAC isn't the cause, it's something within the system itself.

To Reproduce Steps to reproduce the behavior:

1. Load any core, but for this test use the genesis core and play battletoads
2. load battletoads rom
3. Play till you reach the SNAKE PIT stage
4. See intense flickering between the snakes head and tail that isn't present on real hardware.

Expected behavior You will see intense flickering on the images between the snake head and the tail. This flickering stops when you pause the game as well as if you look away from directly viewing the snake tail and seeing it out of your peripheral vision. This of course is not intended so the game is rendering certain graphics at either odd frequency or speed of the pixels. Kev mentioned non-integer rate relative to frame, I'm not sure if that's what is happening since it is doing this on CRT as well as LCD with the ability to adjust integer scaling

Screenshots I was unable to capture the flickering with my webcam or my phone, I simply do not have the hardware to capture the speed at which it flickers

Firmware version JB 7.7 DAC compatable

Relevant Mega Sg settings

Tested on DAC using a PVM 20L5

Additional context this seems to only affect certain pixels or layers or whatever it's doing. Other object are very smooth despite the flickering. It's possible the FPGA isn't recognizing these layers or pixels correctly and giving them incorrect speeds.

[Rageypoo]

Confirmed that the issue is on original, closing!