Error on convert_space and german characters with large files

[Rappi]

Hello,
the following problem occurs here:
When files larger than 4 MB are uploaded, then neither the spaces nor the German umlauts (äöüÄÖÜ) are replaced. The changed file name is displayed in the file manager, but the file is not renamed on the server, which means that you can not view, download or delete the file.
If files smaller than 4 MB are uploaded, then everything works as it should!
Does anyone have a fix for this or an idea where the reason for this might be?
Greetings, Thomas

[Rappi]

Hey,
nobody with the same problem?
All files smaller than 4MB are ok, but files larger than 4 MB not!
Please help