Second time I have seen this , nearly identical symptoms. Problem - Mower starts right up easily, runs approx 5 minutes and stalls out, restarts easily, seems to run fine except that stalling issue, May or or may not be accompanied by a lean surge or misfire. First teardown, find absolutely nothing wrong with carburetor or fuel system, clean fresh gas, everything clear. Trick is to do a "hot" teardown , when the carburetor is still warm and affected by engine heat..
The culprit - the venturi pictured here:
When torn down and carb is still warm/hot , remove the main jet (as if to clean or replace) and tap the air cleaner side firmly on your workbench, voila, the result:
non replaceable, non-serviceable venturi likes to fall out once it warms up, that loose fit allows air to bypass the venturi and you got a lean surge or a stall