Rod, I'd start by testing the polarity of each cab/speaker cable with a 9-volt battery.
First plug a 1/4" speaker cable into 1 cabs input, now get a 9-volt battery and position that same speaker cables other end where the battery's (+) connector is touching the plugs tip, and the batteries (-) terminal is contacting that same plugs sleeve (or side shaft) portion.
As you do this the speaker should move outward a bit (not in).
Now do the same test with your other cab and its speaker cable.
If 1 of your cab/cable tests resulted in a inward speaker movement, swap the 2 speaker cables your using to the other cabs and repeat the same tests on both again to absolutely confirm if its 1 of your cabs or 1 of your speaker cables that was simply wired backwards. (if the other cab suddenly now has the inward speaker movement, that speaker cable is wired backwards / if the same cab is still moving inwards, that cab was mistakenly wired backwards)
Now, repeat the whole same tests again, but this time plug into each speakers OTHER parallel jack to absolutely confirm these were also wired correctly. (each of the cabs dual parallel speaker jacks are supposed to be simply wired together to the same +/- polarity inside)
If all the speaker jacks and both cables test correctly, then it sounds like 1 of your amps parallel output jacks was somehow wired backwards.
ps:
Most all amps with the commonly used dual parallel speaker output jack system (like your LMII has) should also be simply wired together inside (+ to +), and (- to -) just exactly like the dual parallel jacks found on most all speakers.
Let us know what you find.
