Incomprehensible error message after uploads

Hello fellow community members,

For Two weeks now when I upload multiple files on NextCloud I keep getting a error message although the uploads don’t fail. The total volumes never exceeds 1,5 GB and it is in conformity to my NextCloud-settings. The error Message reads: “The media could not be loaded, either because the server or network failed”. This message is strange because the upload itself always succeeds. Please see attached an example.

Please could you give me a tipps on what could be the cause that I receive this message although all my files have been uploaded.

Thank you and best regards