Two notes for the creator:

1) The CD4000 series is about the slowest logic family that's still on the market. Switching to anything else - 74LS, 74HC, take your pick - will improve your fMax dramatically.

2) Every IC on your board needs a decoupling capacitor as close to its power/ground pins as possible. Not having those is probably causing a lot of weird behavior, including the "interference" you're seeing from other devices.