A minus number eg -99 indicates a disconnect somewhere & maybe at the D25 end - when installing the thermocouples/wires I usually
Remove the backshell & the blackheatshrink near it
Carefully bend the harness to the shape needed when it's installed so the pins do not retract back from the fully home position
(note - if you hold the dsub connector, close your other hand around the loom, & wiggle the loom at that end while looking at the end tip of the pins - you'll then see them moving in/out & in come case will actually be recessed far enough to cause a disconnect - try it & you'll see they move like pistons) the egt/cht wires are much stiffer than standard wiring & the movement of the harness can/will result in disconnects.
After the harness is bent (especially the ones further out from the center of the D25) to the shape of it's final resting place you should then use lacing cord to better 'hold' the wiring in place. Then use self amalgamating tap for where the backshell clamps around the harness.
FWIW - I also use electrical contact cleaner on those connectors & at the probe end. No worries