Greetings,
I can confirm I saw something similar, but unsure.
May I ask does this issue resolve if you temporary install the Classic Widgets plugin and temporary switch to using this plugin?
Try out here and reply back:
In terms if something is being blocked or challenged, you can check this by navigating to the Cloudflare dashboard → Firewall → Overview tab and check for the events.
I would suggest you to add the server IP to the Firewall → Tools → IP Access Rules just in case.
Furthermore, before moving to Cloudflare, was your Website working over HTTPS connection?
Can you check if the SSL certificate is still valid at your origin host/server for your domain name?
May I ask what SSL option have you got selected under the SSL/TLS tab at Cloudflare dashboard for your domain ( Flexible, Full, Full Strict … )?
Quick tip: Tune-up your PHP values a bit at your server/hosting provider/cPanel if you can:
memory_limit = 256M
max_execution_time = 300
max_input_time = 1000
max_input_vars = 5000 or 7000
post_max_size = 64M
upload_max_filesize = 32M
Regarding Cloudflare 524 error, may I suggest you to try looking into below articles to troubleshoot the issue: