I can't say I've had this issue personally, but when my brother owned his D2 he made an interesting find in relation to the Option A fix.
While this information was posted to AULRO at the time it seems to have been ignored and/or forgotten, so I've decided to post the information up here.
One of the potential causes of the Three (or Four) Amigos is an dry or cracked solder joint on the "snout" that the Shuttle Valve Switch plugs into.
Option A (2/3rds the way down this page) provides a way of solving the issue by removing the plastic from behind the snout pins to allow the joint to be resoldered. When my brother went to do this fix he discovered these solder joints were fine. Even after a precautionary resoldering the earth connection was still intermittent.
What Steve noticed was that the "snout" could be moved up and down slightly. After a bit of exploratory digging into the external potting he found a second location with two solder connections where the "snout" joins to the circuit board that holds the external connectors. Apparently these two pins had some kind of corrosion and required a bit of clean up before they could be soldered. After soldering these two joints the play in the "snout" was eliminated and solved the connection remained solid even when the snout was wiggled. So if you are planning on doing the Option A fix it's worthwhile checking that the connection remains solid when moving the "snout".
This photo shows the location of the pins and the kind of excavation required to access. The hole needs to be filled post repair but is hidden behind the mounting so this doesn't need to be especially tidy.