Are you seeing DCS signal strength varying within a block? Or, do those measurements each represent a single block?
If it were me I would be trying to correlate the issue to a single TIU. That may mean cycling through the tius one at a time on one of the blocks that shows a weak signal. It could be the signal generators are getting weak. If it doesn't seem to follow any TIU the problem may be in the track or possibly wiring.
I think that sometimes when we build larger, more complex layouts it doesn't really help when things work the first time because we don't learn how to trouble shoot our new layout.
