Firefox freezes in family tree window in Ancestry.com

I have been running "Ancestry.com" on Firefox" for a number of years without any issues. The last few weeks if I open Ancestry to a window that shows a family tree the window freezes and I get a notice that says "This window is slowing down your browser" and it gives me a button with a "Stop" option. When I click the button the window unfreezes for one click and freezes again. This only happens in a "tree" window, the rest of the application works OK. I have done many of the troubleshooting steps, renew refresh, clear cache etc. with no improvement. I checked with "Ancestry" the recommend Firefox or Chrome. Trying Chrome there was no problem. My preference is Firefox as Chrome is to invasive. I am running Windows 10 (up to date), an Asus Z87 Plus motherboard, an intel core i7-4770K cpu and a EVGA GTX 650 Ti Boost gpu with all drivers up to date. I have Firefox set as my default browser. Please advise - Thank You John H ( jrhop@hvc.rr.com)