The fact that this only happens with the Taylor suggests it isn’t the Kemper’s fault. It sounds like the Taylor has a very low output level. Check by plugging straight into the Audio Interface (with out the Kemper) and compare the output level to your other Piezo Guitars. If the output is very low there are three possible causes that spring to mind:
1 - the battery is low and needs replaced (it can still have enough juice to light up the preamp LED without powering the circuit properly)
2 - the preamp is designed with a low output
3 - there is a fault in the preamp which needs repaired or replaced.
Thanks. I think the Taylor pre amp is designed with a low output. If I raise the monitor output by 50% I got a good amount of volume I can work with.