Cubase 8.5 Cycle Problem

Hi, everyone.
I am having problems with the cycle function in C8.5. I specify a number of measures for the cycle, and when the cycle re-starts (=the first time the selected measures are repeated), I lose audio in some of the midi/instrument tracks. Alchemy and Sampletank2 used to do this intermittently, but they would ‘come back’ if I interrupted the cycle and pressed ‘Play’ manually; but today Groove Agent SE4 also did this for the first time, and did not come back. The only way it can come back is if I reload the program (in GA). It is very frustrating. Does anyone have any idea what this is and how it can be fixed?
Thanks in advance