Background video loop stuttering (Vimeo)

Site URL: https://isabel-wilkerson.squarespace.com/

I have a background video loop that's stuttering on Firefox. It's embedded from Vimeo on a 7.1 site (pre-launch). Pretty sure it was working fine embedded from YouTube but we wanted to eliminate the YouTube artifacts floating through from time to time, so we moved it to Vimeo.

I see someone else posted a similar issue here but not close enough to solve my problem that I can figure out.

The site is here:

https://isabel-wilkerson.squarespace.com/

Password: flashlight

Can anyone help?

thanks!

~Laura