The trouble, as I understand it (bear in mind that I’m entirely new to MODx, not experienced in CMS and not at all proficient with SQL), is that my tables did
not use the mod_x prefix (because I chose to leave the field blank during installation, not knowing what it was for... so this was the configuration set in config.inc.php [no prefix])
but a rogue function was insisting on using the mod_x prefix (because it wasn’t doing the requisite call, as you specify -- again, if I understand things correctly).
Since I didn’t (and still don’t) have much clue as to what files/lines I had to (should) edit to correct the rogue function(s), I had to reinstall, taking care of not touching the Prefix field... (So, yeah, to be gentle with newbies like me, in the future, try to use the requisite getFullTableName call...
)
Anyway, those hurdles at least helped me familiarize myself a bit with some parts of MODx...