Is there a wise way to debug a large code?

[Ioannis]

I would try first the software filtering as I described to you.

Last resort to capacitors. If something changes, then you would remove old caps and put new, larger or smaller???

Ioannis

[CuriousOne]

Yeah maybe
My software skills are quite limited as you can see from my posts
And by the way, there was another issue which I've fixed now, and quite likely it was also causing the problems
Due to coding error, I had that brightness adjusting PWM routine called 500 times per second (it was placed in middle dot blink loop)
and when you use HPWM statement, instead of changing the current PWM register, Picbasic stops the pwm generator and restarts it with new values (you can check this with oscilloscope) which causes additional noise generation. Now I moved it into segment refresh routine, which happens once per minute (and keyboard input is deactivated during it), so most likely, it should work without capacitor now, but too lazy to take it apart and unsolder

[Ioannis]

Glad you found the logic error on your code. You did just fine!

Ioannis