If Sentai had a problem with the show, they just wouldn't release it, and return the rights to Japan. The fact that the on line streams have remained available doesn't show this to be the case.
Speculation at Mania forums and elsewhere is that there is a problem in Japan. One idea is that the Japanese distributor has discovered extra liabilities and royalties owed, in particular perhaps down to licenses, copyrights and trademarks in the show, which would multiply the further it is distributed. By limiting physical distribution to Japan alone, they may be minimising their costs.