PCManFM is not chaching image thumbnails

Hi, I installed Mabox a week ago and I’m pretty satisfied, especially when I see it takes only ~480 MB of RAM and returns very close to that value when I close all programs. Also bonus points for the incredible cozy look. Congratulations.

Now about my issue.
I have several folders with more than 2,000 files each and PCManFM v1.3.2 shows them properly, BUT, at the location “/home/USER/.cache/thumbnails/normal” only thumbnails for videos are created and none for image files or pdf files. So every time I open one of those folders, PCManFM begins again to recreate those thumbnails, by the time it reaches the last file in the directory, probably 3 or 4 minutes had passed.
Any idea what I have to tweak to make PCManFM to write those thumbnails permanently in the .cache folder?