Are you doing piece-wise summed price? If so, we recommend constraining price to be negative. Also, with standard summed pricing in ACBC, we generally recommend to constrain linear or log-linear estimation to be negative for the Price slope. This aids considerably in proper convergence.
If it isn't the issue with constraining price, then I'm perplexed, because ACBC usually converges very nicely. Could mean you should have one of our tech support consultants look more closely at your data.