I've just bought a bunch of greyhound races (UK and Australian) from the start of October 2015. Although they show betfair SP, I can't get a SP persistence bet placed either through the main interface or by trying to get it matched by a trigger.
This only seems to affect "SP persistence bets", not bets placed at SP in the first place.
I've just checked and it's affecting USA horseraces too from the markets I downloaded. Also the free greyhound test meetings which came with Time machine
UK races, some of which I bought a few weeks ago, are fine.