I don't think there's any one answer. Dcs can be tricky when it comes to getting a perfect track signal.
The first thing I would do is make sure the tiu's signal generators are actually working.
Hook up a small test and do a signal test on each channel with a know good engine. Should be a perfect 10.
(I don't think there's any other test except the proto-cast feature...playing music )
Voltage... what goes in the fixed channesl comes out. they're a straight through connection.
Testing...... Disconnect the reds (leave the blacks connected) and add them back one at a time (test each time you add a feeder) You may find longer blocks work better than a number of short ones.
Supper's calling.. good luck.
