I've tried VarAC version v3.3.1 with both CAT and OmniRig. With both options my transceiver does not stop transmitting. So when starting a transmit cycle the transceiver is properly keyed-up, but the PTT is not released and the transceiver keeps in TX mode.
Using Winlink or WSJT-X the keying works just fine.
edit: I'm using a FTDI TTL serial cable for cat control. For audio I'm using the the XGGComs Digimode-3-Xiegu interface.