Amazon Photos upload and Safari app cache

Dear all,

I am using Amazon Photos to backup all my RAWs and edited pictures. These pictures are imported via the files app from a SD-card and saved locally in a folder on my iPad (i.e., as „native files“ and not as photos in the camera roll). To upload these pictures I go to amazon photos via Safari and I drag‘n‘drop the files.

Now the problem: Safari seems to cache all these files from upload. Uploading, for instance, 5gb of *.NEFs results in the same amount of additional app size. Currently I have an app size of 38gb. Deleting all „website data“ through the settings does not help. Is there any way to reset Safari without a factory reset of the iPad?

Just in case: an upload through the amazon app does not work because only the camera roll is supported. However, it is crazy that safari does not „clean“ its cache.

iPad Pro 11 2018

IOS 13.4.1

Help is really appreciated. Thanks!