About 5 years ago in 2018 there was a correction made to PowerOLAP to correct a bug which was present related to MISSING or ISMISSING. As a result of this correction, it may require some changes within models related to testing for zero.
Solution
When writing a formula that is checking for a zero on a detail data point, it is required to test for both zero and for ISMISSING() to properly test for a zero value. Please see examples below for how this can be written.
Example 1:
IF(OR( [datapoint]=0, ISMISSING([datapoint]), true, false);
Example 2:
IF([datapoint]+1=1, true, false);