Hi Jon 

Thanks for posting in the community!  Could you try opening your document in a private or incognito window to help us narrow down the potential cause? Could you also try connecting to a different network? Sometimes account performance issues can be related to internet security/speed or browser issues. These steps will help us eliminate that possibility.

If those troubleshooting steps don't help can you please get in touch here and provide the document URL from Lucidchart? Thanks again for posting and apologies for any inconvenience this causes you.