I threw this out in a different thread, sometime back, but am wondering if it could have some bearing on what's going on. It has to do with balanced wiring. Early this winter I rotated the batts one spot clockwise:
before,
B1 B2
A1 A2
... series and parallel cables were of identical length... + from A2, - from B1.
now,
A1 B1
A2 B2
... series cables (A1-A2 and B1-B2) are both 14" long, but the parallel cables (A1-B1 and A2-B2) are only 8" long... + from B2, - from A1.
Could the unequal series vs. parallel cable lengths be part of the problem?