Hi – I’ve asked for some help from the developers. I’ve seen this before, and sometimes a rerun will work at the public servers and sometimes not. Have asked for more feedback about what the solution would be when running a local Galaxy: https://gitter.im/galaxyproject/dev?at=5cd9de66f52a23751628805a
They may reply here or at the Gitter chat. Please feel free to jump in there for more interactive feedback. Just keep in mind that communications are asynchronous, as the developers are from all over the world in different time zones. You may hit a time when they are around, and might need to wait a day or so, depending on where you are
Sharing the version of Galaxy you are running and any special configuration will probably help.