Hello!
As I can see the issue, is unrelated with Cloudflare tunnel 524 to a specific colo.
Checking at the logs, the host reporting 524 errors on multiple geolocations.
I run tests on multiple colos and I can verify here the 524, however that seems to be an issue on the origin side.
Could you just create a simple Cloudflare tunnel and let me know if you can reproduce the issue?