If you are seeing unexpected errors with the Basic Upload tool, we need to take a look "under the hood" to see what is happening.
The best way to troubleshoot is to turn on the browser logging feature, because that will usually show us the problem right away. The procedure varies slightly browser to browser, but its pretty simple.
I'll outline the steps for Chrome, Safari, and Firefox below.
Enable logging on Chrome
Enable logging on Firefox
Enable logging on Safari
Turn on the Develop menu, which is a checkbox at the bottom. This step is required.
Now you can show the error console.
Once logging is enabled, you will see a new area at the bottom of the browser.
Any errors that occur will show up in the Console area at the bottom. You can take a screenshot of the error message and send it to email@example.com.