I have been using the Crestron module for years on my 861v4 and then v6 without problems. I am using a 3 wire cable

I did have a very similar problem to yours some years back. After much frustration I found that it was a flakey RS232 port on the Crestron.

Have you tried using a different serial port?

861v8+ID41 Revelation One filter, HD621, Musical Fidelity M8 700 mono blocks, Focal Scala (x2), Focal Mini Utopia (x3), Velodyne DD18, Oppo BD105, Roon NUC, 218, Radiance 2021, JVC X9000