I wonder if the Texans failed him on purpose so they get higher draft picks. Same thing happened some years back with the Browns and John Moffit. Actually I just googled it:
Moffitt was traded to the Cleveland Browns on August 19, 2013.[9] On August 20, 2013, the trade was rescinded, reportedly due to Moffitt failing his physical.[10] In an interview with 710 ESPN Seattle, Moffitt claimed that Cleveland wanted him to take less money to play there and when he said he wouldn't do that they told him that they were going to fail his physical.
So I im sure the Texans did that on purpose. Seems like a shady thing to do, unethical at the very least.