Air in glycol lines -- loud glycol circ after new valves installed

[barleyfreak]

I recently replaced all my solenoids with actuated ball valves on my FVs. Had a local plumber reattach the PEX drops and hook up the new valves. Since then, a couple of the FVs when the jackets are running are VERY loud as the glycol circulates. The efficacy is not a problem. They chill just as effectively as before, but I am wondering what is making the loud sound -- is it air entrenched in the runs? It does not do this on all the FVs. Again, the cooling is fine, just this very loud sound on 2 of my 6 FVs when the glycol is circulating.

Thanks,
Dave