With the scarcity of information about the layout configuration of the equipment in use, it's pretty hard to offer any concrete advice. One observation, switching remotes for the issue you mentioned is pointless, it clearly seems to be a DCS track signal issue, not a remote to TIU issue.
You might start with the exact model of the locomotive, the hardware and software version of the TIU, and the size of the layout, that would be a good start. Also, have you tried other DCS locomotives on the same tracks? How about setting up a few feet of test track and connecting a TIU channel directly and see what results you get? When you try something, you need to be specific as to the exact steps you take.
Remember, the folks in this thread are doing this in ASCII, so you need to be their ears and eyes if you expect positive results.