Hi Andrew (@mlapl1),
I’ve checked with support and looked through previous issues. There was one issue in v12 where this would happen if you published with the protect content option checked. That was fixed previous to v17. Maybe it has to do with your title as Carl suggests?
If you have an minimal example title where you see the problem please post it here.
I assume you are seeing this in Chrome, as Lectora run mode is Chrome based. Let us know if you have tried it in multiple browsers.
Thanks for reporting this, look forward to helping solve this!