SNES:Scrambled Screen Issue
You may encounter an issue where your screen becomes scrambled as if sync is lost. This is a hardware issue with your SNES having a weak clock signal. Early models of the FXPak Pro may make this issue more prevalent, as described here.
Video scrambling as shown below:
Apply a Dual Frequency Oscillator (DFO) mod to your SNES or a de-jitter mod. Either one will strengthen the sync signal of your SNES to normal levels.