"Bad Request" when sending two grading requests from the same browser (picture included)

[ghost]

When I open two projects to grade at the same time (i.e. I command-click two projects, so I've got two tabs that are both open at the same time), if I click to grade both of them, I get the following error when clicking grade on the second one. I need to reload the page before the second grade to get rid of the error. It's not a major issue by any means but figure I'd add it here. Let me know if I am unclear about the error.

Here is the error: