Need help with ASR33 tape reader - major frustration!

I can't get my ASR33's tape reader to stop missing occasional characters! I have lubed it and tried setting it according to the procedures in the manual but that is very frustrating since many of the adjustments interact. Using a test tape punched on the same TTY with 72 printable characters per line (incrementing from space through Z and punctuation, then LF + CR at end of each line), if I carefully adjust the detent position I can achieve one (and occasionally 3 or 4 in a row) "skipped" characters about every 10-20 lines which is roughly once every 1000 characters on average. I can load short tapes like the BIN loader and then the second short section of 4K FOCAL successfully, but the long first section of FOCAL (which takes over 10 mins. to read in) invariably gives a checksum error. In other words, not good enough. The missing characters are not being read into the data stream at all, nor are the previous or next characters duplicated. I wrote a program to just read the characters into the AC and halt if a NUL (000) is read. All 0's are indeed being read on the missed character and I think this is because the contact pins are all held down if there is a "misfeed" where the tape moves just enough to put the pins between rows of holes, but not far enough to skip to the next. Anyone with experience "tuning" this beast, please give me a hint! thanks Charles