This shows the back of the R220 shift register before and after I fixed it. On the before picture I've labeled the solder blob that was shorting pins that shouldn't be connected, brown flux residue from a previous repair, and where a previous maintainer wrote the letter designation for the connector pins. On the repaired board I labeled the two components replaced. The re-soldered connections are shinier though the picture shows them as darker.
The short was D1 to D22 on the capacitor side. It seems like that should have caused problems, though since the short looks like it was from when the board was made, it probably wasn't making it fail. D43 may not have actually caused the board to operate incorrectly since the input pin R is grounded and the diode was still mostly working in the forward direction.
Schematic for this board
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