Why do unplayable clips appear when I set the number of girls plays more than 6...?
When the number of plays is 6 or fewer, I can play any clips I choose..
Is this a problem with the spec of my PC?

In my limited experience and with my hardware the most limiting factor is the lack of raw processing power of my CPUs, and that's usually playing just one card. So I would guess it is a PC spec problem but there may be some things you can do to improve performance like closing programs your not using. Other Members may have some tips in this area and it would help to know what your hardware is. 😕 😎

@hashin007
The software is a 32bit app so it cannot manage over 4GB of RAM. If your shows are in 4k, the size of 6 or more clips and the softwares in background can be higher than 4GB and the app is not able to play them.