Only foam after moving keg

[BrokenBrew]

This seems to happen whenever I move a keg that is 1/2 or less full. No matter how carefully I move it, afterwards it pours almost all foam. The only way I know to fix it is depressurize the keg just before I pour, and just let the beer flow really slowly.

Anyone else see this? This seems to only happen when I move a keg.

 

[balrog]

Possibly stirring up sediment which is tiny fine particulates that become perfect nucleation points for CO2 to come from solution. But I've not noticed that, even with WY1007 or WB06 which are considered "powdery" strains.