A few days ago I found out that there were two files called thumbdata3 in "DCIM/.thumbnails" that were occupying around 6 GB between the two. I deleted them, and did the workaround of creating folders with the name of the files. After doing that, the files haven't been created again, but the available space hasn't increased. Before deleting the files I had 750 Mb, and after deleting them I still have the same amount of space.
What should I do to recover the amount of space occupied by those files?
I have a Xperia Z3+ with a stock ROM (5.0.2), unrooted.