The world is one ive downloaded from the aternos after playing on it, and ive kept it as a zip form. Ive then gone to upload and tried uploading this world. Error 105. Tried an unzipped version;Error105. This "save" was called "world(2)". Ive renamed the zip to just "world"(without the ") , and got error 198, but worked on the second attempt. So in conclusion, looks like the file name did the trick.
Im using windows 10; set to german.