If I'm not mistaken, that is a retic??
I'm VERY interested in seeing responses to this thread. Thats exactly ONE of the things mine was doing before I lost him. Other symptoms were swimming erratically around the tank, seemingly with no control. When moving across the bottom, it almost looked like he had a "limp" He would also at times roll his disc down creating a hood shape, but far more than usual as when they are feeding.
That doesn't look like what I'm familiar with when it comes to death curl. I've only seen it once, but she curled and would NOT be able to put her disc back down flat. Of course, check the water parameters. With mine, my retic was acting like this while my two hystrix were absolutely fine. My water checked great with each test I did.