Contention for M7 Motion Chip?
There's no contention. Apple provides APIs for accessing the M7's data and all the APIs are thread-safe. This means that there can't be any problems caused by two apps accessing the data at the same time.

Furthermore, reading data from the M7 doesn't manipulate the data in any way. Other apps can still access the data and the data is not reset.

As for the cause of the specific problem in the question, I'd put it down to a bug in the app itself.