Hello,
Thanks for your patience, It seems you have issue with Woo and WordPress REST API, Could you please install following plugin https://wordpress.org/plugins/disable-dashboard-for-woocommerce/ and navigate to the WooCommerce -> Settings -> Advanced -> Disable WooCommerce Bloat then try to save page and check all your pages in your dashboard and let me know if it solve your issue or not?
I’m looking forward to hearing from you.
Regards