I have been experiencing some guiding issues with my QHY5L-II mono with I was unable to resolve. The camera would hang erratically after maybe 2 hours working, disconnect, take 5 seconds to download the image and so on.
I explain my problem on the QHYCCD forum and the answer they provided solved my problem completely. I have used the QHY5 for 3 night now and no problem whatsoever to report.
Here is the link to the solution to my problem.