For those following this, we're able to now send tests and review/send by clicking on either button multiple times consecutively. Seems like this issue could be related to a change made recently to the link checker.
We've heard several reports of this issue and we are actively working on a resolution. Once a solution is in place, I'll be sure to reach back out here to let you know. Thanks for your patience on this and our apologies for any inconvenience.