Trying to get HRM Map but the timer gets stuck after a couple of seconds...

[311Gryphon]

I've done several missions where I've successfully gone from RBM to a good HRM Map and it seemed to work as it should, and as shown in several of the videos I've watched.  Today I jumped in a mission and have tried several times to get a good Map but after activating the Map Cursor Function the timer starts to count down, but stops after a 2 or 3 seconds and won't continue.  I'm curious if anyone else has run into that issue, or if anyone knows if it's just something I'm doing wrong.  Here are the specific things I've done so far.

• Put Target point within a few hundred meters of my target
• Flew with Target Point about 35° off my port side, straight and level
• Took Command of A/G RADAR as pilot
• Set Cursor Function to MAP
• Slewed a 4.7 (I think) box over the Target Point
• Ensured it was not disabled (X-ed out)
• TDC Press to activate Cursor Function
• Scope went to the HRM and map counter started counting down
• Stopped after 2 seconds
• I reset to RBM Scope and tried again with same results
• I reset to RBM, changed my angle to be closer to 25° and tried again with same results
• Same but at an angle closer to 40° with same results
• Same tests but closer
• Same test from WSO seat

It may just be this mission or the mission location or something, but there should be plenty of contrast at this location.  And now that I think about it, my RBM scans are trash.  That doesn't seem to be working as it should.  Flying along the ocean with a relatively flat desert seems like it should at least show a clear delineation between the ocean and land, and it does on the first sweep.  After that the scope just fades to black and subsequent sweeps do nothing.  I've tried to adjust brightness and contrast.  I'm not sure if that's related though because I had that happen on a mission last night where I was able to get good HRM Maps.