I wouldn’t think you’d hear audio in the TX speaker only in the RX speaker. Maybe that’s what you meant to say.
I’ve never set up a RICK based GM300 repeater but I bet plenty of folks around here have. So even thought the forum is about using app_rpt maybe some one here will help you. I suspect the problem is programming on the accessory connectors. I have set up a few CDM’s (which aren’t much different than GM300s) as repeaters and you do have to program the accessory connector pins for audio. Preemphasis and deemphasis are not the problem. That would only make the audio tinny or basey.
I did a quick Goodle search for site:www.repeater-builder.com RICK and got lots of hits. So check that out. Repeater-builder (both site and list) is the goto place for this kind of stuff.