BQ76PL455A-Q1: OVERSMPL 32 x CMD_OVS_CYCLE = 1 won't respond?

Part Number:BQ76PL455A-Q1

I hope I'm keeping you busy with all my questions ;-D,...but here goes yet another -  When OVERSMPL = 7D (32 samples each channel), my results are good. But when I reprogram to FD (32 samples, 1 per pass), the AFE stops responding. When querying its registers, they all report correct (OVERSMPL = 0xFD), but it won't reply to my read ADC command. Resetting it back to 7D gets it running again, or 0x7B as well....just on 0xFD ???

Thanks again in advance!