Hi ! I had the exact same issue in the past and experienced it yesterday on the flashpoint server.
I managed to reproduce the bug several times in a custom mission editor scenario.
During the scenario, I do a cold start from batumi, take off, turn around and look at a waypoint placed on the kobuleti cross. Before proceeding to the cold start, just like I did yesterday on Flashpoint, I asked the ground crew to :
update the INS coordinates
remove the AR probe
remove inlet covers and ladder
I did the exact same process 5 times in a row to see if the issue was random but the bug happened every single time. The pod looks at the correct coordinates, but it jump elsewhere as soon as I press or slew the TDC.
Since I usually never ask the ground crew for an INS update, I tried once again but this time without asking them to do so and the pod had no issue on this run and I was able to slew smoothly without it being jumpy.
Since DCS didn't record the trackfile previously, I jumped back into the game to get one. I created a similar scenario quickly, and managed to reproduce the bug one more time after asking the GC for an INS update.
TL:DR : WMD-7 jumpy behavior seems to be tied to asking the crew for INS update via the configuration pannel.
I hope those info and the trackfile can help.
JF17 TDC bug.mp4
LastMissionTrack.trk