As in #3299. It happens (as far as i can see) only if the "pipe" is very long but now there are even two different configurations (both happen w/o optifine aswell):
a) angle dependent:

b) distance dependent:


(Farther away renders correct)

Fixed in 8.0.x by #3384

This requires pumps to render in the TESR rather than with an entity. No idea if this will happen in 7.2.7 or not.