Low fluid would reduce pressure enough to cause the problem as well as other problems ALL the time. It wouldn't be it does it this time, but not the next time...it would do it all the time. I have ran Auto's my whole life going back to B&M Autos in the 70's. Valve bodies require fluid to build pressure as anything hydraulic. It is not going to be intermittant. Just my take on it..and I have had zero issues, except not shifting quick enough when I want it to, but t hat is just the programming... Unless this guy has a noticeable leak, not fluid in my opinion...