Master unit not beeping after reading SI11 cards

Somtimes the card itself will blink but can't seem to make it blink every time. Not sure what is different about SI11, I have tried to look at MeOS and how it handles ACK of SI11, but can't find anything different. This might also apply to SIAC.
The issue starts after reading data from the card. Before running read_sicard(), ack_sicard() works fine on SI11.