Good questions @olatun. Not sure about one VCA developing a fault. If you run both VCOs leading into the VCAs off the same clock the clock should keep them in sync. Do you have more details for me?

I don't have a good guide for using and EQ. I am sure there are ones out there. I think a lot of EQ learning is through use. Find the sounds you like. Setting an EQ is also very different for every instrument. I recommend playing with it as much as possible and you will develop your own techniques.