Quicktime Skip after fast forward
Found a partial solution. As it appears, running 'purge' command from the terminal fixes the problem. This is not the ultimate solution(), but it gets the job done. 

Also I should note that another fix might be to use CMD + T(Trim) - I've heard it helps, but I usually use Quicktime to watch videos online, which this feature is not available when streaming videos.

Cheers.