When I had this issue, it was a signal problem. That was years ago and I struggle to remember it fully. I have an older TIU that still works fine! So it may not be age as much as what it's gone thru.
Several DCS versions over the years had bugs. Those kept me on my toes and improved my troubleshooting skills! We have to narrow down the problem further.
For further help, we need more details.
What version of DCS software is in each component?
What is your power supply?
Do you have any bulb or filter attached to the track or TIU output yet?
Does the lagging go away if the units are tethered with a 4 wire phone cord?
