RTC - eclipse client - error: no more developer floating licenses

Occasionally when users try to accept change sets, they get the error below.

 Reason: Your license or license setup doesn't allow you to modify a repository workspace. Reason: An error response was received from the Jazz Team Server. Status=400. Message: CRJAZ1286W No more floating licenses are available for use. The "Developer-Floating" license that is currently assigned can do the operation, but no more of those licenses are available for checkout.

So obviously it would seem that we are running out of floating licenses, however, when we run the report on license use it shows that we aren't hitting our max usage.

Any ideas what could cause this?

Thanks,

Dan