Hi… As an additional data point, I did see a response from the other little guy (e286033c6e39d8) when I tried:
$ curl -H 'flyio-debug: doit' --head 'https://ticketing-remix-fbe1.fly.dev/'
HTTP/2 200
x-fly-region: lhr
strict-transport-security: max-age=3153600000
content-type: text/html; charset=utf-8
set-cookie: toast-session=e30%3D.; Path=/; HttpOnly; SameSite=Lax
vary: Accept-Encoding
date: Thu, 15 Feb 2024 23:50:27 GMT
server: Fly/17d0263d (2024-02-15)
via: 2 fly.io
flyio-debug: {"n":"worker-cf-ewr1-ed97","nr":"ewr","ra":"2605:<elided-ipv6>","rf":"Verbatim",
"sr":"lhr","sdc":"lon1","sid":"e286033c6e39d8","st":0,"nrtt":99,"bn":"worker-cf-lon1-d88f"}
^^^^^^^^^^^^^^
fly-request-id: 01HPQJVF35X74Y07PN7JP3PHSF-ewr
(Formatting altered slightly and emphasis added.)
This part might be related; in (at least one episode in) the past, it’s turned up when an underlying physical host was approaching overload, 
…