Doing Works In Pc can give wrong results When Cracking
For example hashcat works and i watch a video 

can it give wrong results?

For example cap files pass is 11111111

I watch videos and is it possible hashcat cant find ?d?d?d?d?d?d?d?d

This affects only cracking speed?

Doing other things on the machine that is running hashcat will not produce incorrect results. It will only reduce the speed of cracking.