Contao creates copies of MooTools to the /system/tmp folder but does not delete them

Contao 3.2.0. Contao creates copies of MooTools to the /system/tmp folder but does not delete them at any point. When I noticed that had happened, there was like 45k copies of the same file. I need to know where in the source code is the part where files are copied to tmp so I can take a further look. Also it interests me why a copy is made in the first place and if there is a way to disable it. This issue only appears on one specific Contao installation I administer, and it was upgraded from version 2, so it might have something to do with it.

Are you sure it's Contao itself and not an extension? Contao 3.2 handles assets in the "/assets" folder.

You may want to run the Contao check to verify the integrity of your Contao installation. Then, enable the "Safe mode" from the back end system settings, purge the temporary folder "system/tmp" in the "Maintenance" module and keep an eye on the mentioned "tmp" folder for any unwanted file copies.