These powerheads are AC
and not direct current, so there's a 50/50 shot of the PH wanting to start in reverse.
I had the same issue before I realized a cage was on incorrectly. I now also run the Koralia wave maker with 2 1400 evo's in my 55, and since I replaced the cage have had no issues with running in reverse. You will, however, hear a clicking sound the times they do want to start in reverse., as the blade will bounce off the bumper. I have mine set to switch between 1 & 2 every 3 minutes and have not a single reverse start up for the 2 months I have been running it. So just make sure the cages are on properly and that the rubber bumper piece does not fall off. I saw online replacement cages for just a few dollars, so maybe buy a couple for back up, even though I have not needed to replace mine since...