We've seen an increase in these errors for transfers with video files in them.
Please make sure the video is completely rendered, is not open in the background on another program and is completely finished exporting from your video software to your computer before you select the file for transferring.
An easy way to ensure this is by creating a .zip folder from all of the files together and upload that instead.
Also, if you select a file for uploading while it's still being edited (for example: being copied to your computer, before saving it, or before moving it to a different location), our uploader won't be able to get the correct information about the file's size, which can cause the behaviour described in this article.
To avoid this, don't fiddle with your files after selecting them for a transfer. Transferring from an external hard drive or USB stick can cause this problem as well.
If you continue to have trouble, just reach out to our Support team for more help!