2008 h machine giving low flow error after 30 - 40 minutes for 2 to 3 cycle and then afterwards ok. this is repeated after every 30 minutes. flow motor pressure is ok in calibration mode. but in dialysis mode it drops to 8 -9 psi on 500 flow.

Check both deaer and flow motor brushes. they may be worn.

if the brushes are good try replacing the pump head