Had another never-seen-that-before error today. Thought I'd document it for posterity.
I had a few brand-new KRC4s that were being powered up for the first time, after delivery from KUKA. As expected, I got the "RDC/Hard Drive mismatch" error, and told the robot to use the RDC data. But unlike any other KRC4 I've started up recently, these robots gave me a persistent Error 276, "Wrong Machine Data for this robot type".
Now, these robots were identical to the previous batches I had started for this customer (same robot models, same TPs, etc), except for two things: these new robots were running KSS 8.3.42 (the previous robot batch had been KSS 8.3.39), and the robots were configured for 380VAC (no transformer under the KRC).
KUKA Tech Support's first suggestion was to open the active project on the KRC in WorkVisual, delete the robot, then add the robot from the correct Catalog (the 380V catalog, in this case). But this didn't do any good.
After sending out a KRCDiag, it turns out that, for whatever reason, $ROBTRAFO and $TRAFONAME didn't match: $TRAFONAME was "#KR210R3300K ULTRA C4 FLR 380", but $ROBTRAFO was missing the "380" on the end. For whatever reason, selecting the correct robot in WorkVisual seemed to update $TRAFONAME, but not $ROBTRAFO.
The solution was simple: bring up $ROBTRAFO in the VarCor, and set it to $TRAFONAME. As soon as I did that, the error vanished -- I didn't even have to reboot.
Since I've never had this happen before, on KSS 8.3.2x-3x (for multiple different voltage settings), I'm guessing that this is related to KSS 8.3.42 -- it's the only common factor across this batch of robots that's different from all the prior batches. My manuals barely mention $ROBTRAFO, except to say that its the "RDC-side copy" of $TRAFONAME, and the two have to match.
So, anyone getting brand-new KRC4s with KSS 8.3.4x might also run into this issue.