When using fully upgraded After Effects (latest version, I got prepaid CC complete pack), I've got an issue when using spacebar for preview. Sometimes, even though there is space on RAM and the program can cache the preview easily, something goes wrong, and instead of starting to cache the data for preview, After Effects does nothing and on spacebar or numpad0 press goes back one frame. Meaning when i press spacebar or numpad0 for RAM preview, AE doesnt start rendering, it just moves the timeline position one frame backwards and one more frame with every press of spacebar/numpad0. It will continue to do this until restarted. It did this in former version as well, afaik 2015+.