This is a very minor bug, easily fixed through use of AvoidNil, but posting the solution here in case anyone else runs into it.
Tested with Buffer (String) and Buffer (Value) in 86Beta30.
If you feed a Nil value to a Buffer node on the Set pin it will give a Nil output, which seems fine. If you give it a normal value on Set pin it will recover.
However if Buffer has a Nil value at the Set pin on startup of vvvv then the Buffer will turn red and in Renderer (TTY) you will find divide by 0 errors. You can only get it back to normal by deleting the buffer and rebuilding (Or deleting and then undoing with ctrl-z)
Hard to find for me because the nil value was coming from a TCP node. By the second frame after startup TCP was connected and giving me a value so I didn’t know that it was sending nil to begin with.