Now that you have gone back to 1.3.6. It might be worth now upgrading to 1.3.7 again and maybe the upgrade goes more smoothly with the extra resources.
I had a similar issue importing templates (not pages) due to high resource usage that I don’t think has been addressed yet. And when you get the chrome error - click wait. You might have to do it 5-10 times but if you get it to load once then the browser might cache it for the next time. I appreciate it does not solve it, but could be a workaround until Timmse comes along to help.
Also just out of interest remove the homepage from the settings>reading homepage to a another page and then try but then go back to pages and try to open the old homepage that wont open now as in your picture.
I re-upgraded to version 1.3.7 and still can’t solve the problem.
And it’s not just the home page, every page is uneditable. Before that (version upgrade), there was no problem.
I’m going to reinstall the whole WordPress. this may be the fastest solution.
I cannot see reinstalling WP will help but i guess you can try and at least discount it from that being the cause.
But i would send an email to help@bricksbuilder.io with your a temp login link and a link to this thread. They will be able to investigate further for you