Thank you (as always!) mcbee, that's a very detailed report.
I've been on BF's forum to see what the rumour is and it looks like the API has indeed been faulty starting from Feb 13. That's so strange as out support was working on triggers yesterday and today and didn't notice anything unusual (was it luck??). Perhaps it was happening just for users in some countries.
I myself left MF Pro working overnight in AUS races and in the morning all the markets were settled as usual. Hmmm... :-/
Anyway, I'm going to leave triggers placing bets below minimum working tonight, to see if I can catch any unusual API behaviour and record it. I do very much hope I won't be banned after this!
BTW, should any problem with betting below the minimum arise, we are not even in a position to complain as this kind of betting is strongly discouraged by BetFair.