Volvo 960 transmission diagnostics

I bought this volvo a couple of years ago, and as along as I've owned
it it's had periodic tranny error light woes. The light used to come on
rarely but over time now it comes on within a week of being reset. I've
cleaned the W-S-E switch connections and flushed and filled the tranny
with new volvo fluid etc. shortly after initial purchase. When the
light used to come on there seemed to be no noticeable change in
shifting but now when the light comes on it seems late to shift/like it
slips. The codes I pulled up this last time are 5-3-2, 6-2-2, 5-1-1,
and 4-2-1. The 4-2-1 is a battery warning probably nothing to be
concerned about, just that the codes took a while to read. But, the
other codes were not recognized by my machine, anyone else have any
ideas? The sensor and such are a little expensive so I'd really rather
not just start shotgunning parts.