Likewise - and similarly can’t identify the actions that cause it to happen. One further observation - closing and reopening Rapidweaver seems to make the offending page behave again. I haven’t had to duplicate and delete as you have.
Yes - this morning’s episode was solved with a reboot of RW (not just the project). Last time it happened I think (but am not sure) that it didn’t solve the problem - however I my have only closed the project.
Out of interest, what macOS are you running? I’m still on High Sierra.
I have been having at least one RW crash every day.
Have noticed a couple of times that, when going from one page to another in Edit mode, the Loading Stacks dialogue flashes - as when you first load RW.