Rapidweaver is slow after 6.3

Ever since upgrading beyond 6.3, Rapidweaver has been slow with lots of spinning beach balls. I tested 6.3.1, 6.3.2 and 6.3.3 and its get progressively worse. when selecting different pages, to dropping images in stacks to just quitting the program. Sometimes I have to force quit. I have a heavy site with over 100 pages. Is this a known issue and will there be a fix for it. 6.3 and down to 6.0 is fast and smooth

I’m running 10.10.5 on a 2013 Mac Pro.