Oftentimes when time remapping or reversing layers in AE, it will display the wrong frame or sometimes no frame at the in point of the layer. Some things I've done to fix this are extending in in point back, moving the layer, duplicating the layer, precomposing, purging all memory and disk cache, and quitting and returning to AE. These techniques sometimes work, but more often don't, or will work for a while and then randomly not work. The only thing that works consistently is rendering out the precomp and importing the render back into AE.
The video on the link below is an example where I had a precomp with a simple timer. You can see that AE would not display the frame that says "DOWN 50" with the layer reversed