Delayed Key-off in Duplex mode

[KJ7IEG]

I am using STM32-DVM with 2 Kenwood radio as a duplex repeater and running DMR with Pi-Star 4.1.2
I notice that since I switch it to Duplex from Simplex, the transmit radio will keep transmitting for a few seconds after the source has stopped talking. I don't know what is being transmitted when DMR Network has send end of call. However, this created an issue. During the net, when people key up next to each other, the transmit radio will never key off and eventually hit its time-out-timer of 20 minutes. Is there a way to make Pi-star key off rightaway when source key off?