I don't have a Top Tier stand, but I use all-Blichmann kettles, with Blichmann false bottoms, for my mash tun (15 or 20-gallon depending on the beer) and boil kettle. Also use a March pump for RIMS. I recirculate on a Blichmann burner, directly heating the mash tun.
For the first five or six batches, I had symptoms of a "stuck mash", where the output of the pump back to the top of the mash would start to sputter and seize, then eventually crap out altogether, as if it was trying to draw more wort through than was getting through the false bottom.
More playing around has lead me to a different theory, i.e. that the flow rate was too slow (valve on the output of the pump was closed too much) and the burner was too high, which was allowing the wort underneath the false bottom to overheat and actually start boiling, which in turn allowed bubbles from the boil to get drawn into the pump causing it to seize and lose prime. Even when the burner flame is very low.
Opening the valve on the output of the pump (probably somewhere in the vicinity of 1/2 open), and keeping it there, has solved this problem completely. A higher rate of flow means that more wort is moving across the bottom of the kettle and does not get hot enough to start boiling, but not enough to clog up the false bottom. I let the pump run continuously at a constant and fairly healthy rate. The Blichmann false bottom can take a healthy flow of wort.
I wish I could see underneath the grain bed to see if this theory is accurate, but for me it explains what was happening, and the solution.