Motor stumbles when gas moves around in tank

Husqvarna Model 060311M 023782

After carburetor replacement, the engine would surge.

I removed the idle jet from the carb and drilled it out with a very fine drill bit.

This corrected the idle surge.

New problem is that when I push the mower back and forth quickly, or when I come to a stop against a fence or something, the engine stumbles and then regains a steady idle.

It seems the movement of gas in the tank causes the engine to stumble.

Any ideas?

Motor stumbles when gas moves around in tank