Well I meant if you checked the signals using LEDs or logic analyzer.
I use LEDs + 4.7k, tag them to ICs or displays using just a little solder.
Maybe you can slow down the software, and then you can see specific flashes,
otherwise also they should be observeable to light up for an instant.
I often had trouble with PIC ICSP in past years, or tristate/alternate pheripherals,
tagging LEDs cleared that up.