Two different shops were unable to get the Pachyderm's battery compartment door to latch properly. The catch was either not high enough or not in the right position. Or something. The last place literally told me it could not be fixed because it was "broken".
I decided to get heavy-handed and jury-rig something myself. In fiddling with it I discovered that the latch was loose in its mounting and free to move around, i.e. away from the catch. I tightened the bolt that secures the latch, et voila! No longer "broken".
I really shouldn't be so pleased with myself for being smarter than somebody who became an RV mechanic because he got passed over for assistant manager at McDonalds, but I am. Also the battery compartment door latches now.