Strange problem not getting TYT radios to handshake

[N7GWA]

I have a 70cm multimode repeater on a hilltop running Dstar and DMR, utilizing a STM-32DVM V4 board paired with a Kenwood TKR-850. This repeater works flawlessly with all radios.
I am building a second repeater for another hilltop using a STM-32DVM V3 board paired with two TK-8180’s, and am having problems getting the TYT radios to work. The two Anytones I’ve used for testing handshake very quickly, and work great. However when using a TYT with the repeater, it will not handshake, nor will it pass any audio through the speaker during a QSO, but the LED on the top of the radio will illuminate indicating it’s receiving.
All programming parameters on both the TYT and in the pi-star have been checked over many times, as we have spent countless hours trying to figure out how to remedy this.
When the TYT is keyed, live logs in the pi-star software indicate “Downlink activate received from “my callsign””, activate the PTT on the repeater, and sends out data pulses (which the radio visually indicates its receiving).
For what its worth, this has been tested with several different TYT radios, with different people programming them. One person even indicates they had this issue with a Motorola radio.
Levels on the modem have been tuned using a $30,000 Anritsu analyzer, and are as spot on as it gets. No luck with this, so we started messing with both the RX and TX audio levels both in the software and on the modem to see if throwing it off a bit would maybe get it to work.

One thing i’ve noticed, is that the handshake pulses on the Anytones seem much slower than the pulses on the TYT’s. Not sure if that makes a difference, but was an observation.

Completely lost… has something changed with the version 4 board that is allowing the TYT’s to work?