It turns out the second bot was never operational.

That's not exactly correct. The second 'bot' (the Hive account@x-1pob-3vyb account) did distribute all its VYB tokens (99,999 VYB on a 1:3 POB:VYB ratio). It's just that everyone who claimed those VYB did so by sending their POB to Hive account@x-1pob-4vyb and including 'market' in the transaction memo. The 'market' memo indicated their willingness to accept the next-best exchange rate (which, in that case, was 1:3 instead of 1:4).