This radio does have an internal duplexer so I would need to open up the radio to check the connections.
In my experience, depending on the split between TX and RX, the atypical internal duplexer for VHF is a POS unless you have at least 8-10MHz of TX/RX separation.
A repeater's performance is HIGHLY dependent on the quality and tuning of the filtering system.
I shutdown the repeater and connected the antenna to my VX-150 2m radio and using 0.5watts I was able to access repeaters from distances that I had never been able to reach before. I was talking to people in town on simplex and they could hear me well they were talking back on handheld.
And of course this would work well, as you aren't keying a transmitter into the same antenna while receiving.
The duplexers and other filtering and choice of feedline/antenna become
critical when you want to use the same antenna to transmit and receive simultaneously.
Find a local friend who does have a service monitor and other tools to check your repeater.
^^This.
Getting a repeater to work properly requires a service monitor with a tracking generator, and the right combination of filtering (duplexers/pre-selector if needed) and good quality feedline and antenna.
LMR is not the go-to for duplex operation.
Without the right tools and equipment, you are peeing in the wind. Try to reach out to someone in your area with the right tools and skills to assist you. It is not something that can be accomplished on an Internet message board.