In past we had a similar issue while interfacing our (then) Plant-Vesta Standard system to an Orbacom TDM150 radio console. For our system the headset audio is arbitrated through the Orbacom system. The solution was to learn from Orbacom that their system needed to see -10dB or better from the Vesta RIS (radio interface subset). Each RIS box had to be adjusted to between -9 and -10 dB into the Orbacom. The Orbacom CIP trays had to be individually adjusted as well. This removed about 85-90% of the issues. We also added Plantronics H-31CD controller headsets which further resolved the issues. Best luck.
Mark