Slower Max Feedrate after updating Marlin (skipping steps)

I recently update from Marlin 2.0.x to Marlin 2.1.x, and now my max. feedrate before it starts loosing steps is only of about 100mm/s (compared to previous 300mm/s).
Acceleration and Jerk settings are exactly the same as in my old config.
To test max. feedrate I did:

M203 500 ; To set the maximum feedrate to a large value (more than what was tested)
G1 X180 F1200 ; In this case, move x from 0 to 180 at feedrate 12000mm/min (200mm/s)

With the old Marlin version uploaded, the X-axis moves fast and doesn't skip steps, but with the new version it skips steps. My stepper drivers are DRV8825.

Any ideas of what could be wrong? Should I post a bug report?

Thank you

Are you running a Mega1280 or Mega2560 based board?

Bug report 25117 has been talking lately about problems with AVR based boards. As I read it some were able to get close to the old speeds by disabling S curve acceleration.

Thank you, the bug report sound like a complicated issue, I don't even understand most of it (not that I know much of marlin either).
I have a:
-MKS Gen 13 with Mega2560
-S-curve acceleration is disabled
-Input Shaping is disabled
- I still use the old CLASSIC_JERK
- My Marlin version is 2.1.x PatchedSource (downloaded on the 21-01-2023)
Stuttering/Skipping steps also happens with very slow accelerations.

I attached my (already quite a bit modified) config files in case it's useful.
Is there any simple testing/reporting I can do, or should I just rollback to something like 2.0LTS?