Error when I try to upload the video on order

[majeey]

Hello, I need help. After the video is uploaded on order page I got like 1 second to click deliver before I get an error. It's not a problem until I have to attach more than one file. The videos are not uploading at the same time, so when the first file is uploaded I get an error and it's impossible to send an order with more than one file attachment.  Thank you in advance for any help.