When we start Pega on a Samsung Android Tablet, it is not recognized as a tablet. This implies that pxRequestor.pxDeviceType is Telephone, pyIsTablet evaluates to False, and pyIsMobilePhone evaluates to True.
This is wrong of course, and leads to undesired behavior.
Which version of Pega is this for? Are you running Pega in a mobile browser or running a native app?
My recommendation would be to remote trace the requestor from admin studio, and see if you can find both the pyIsTablet and pyIsMobilePhone when rules in the trace. Then, open these rules in Dev Studio and check the conditions. See if you can determine which conditions in the specific when rules are returning true/false. This should hopefully give us some clues as to why the when rules are returning the way that they are.