Cloudflare returning 503 before hitting the target endpoint when using websocket

I’m attempting to implement websockets that connect from one zone to another, specifically from deco.cx to decocdn.com. I’ve established a CNAME from shop.deco.cx to sites-decoshop.decocdn.com. However, I’ve encountered an issue when trying to use websockets directly from shop.deco.cx to sites-decoshop.decocdn.com, I’m receiving 503 without any further information, can anyone help on this?

Working: wss://sites-decoshop.decocdn.com/live/...
Not working: wss://shop.deco.cx/live/invoke/...

But shop.deco.cx is just a CNAME to sites-decoshop.decocdn.com (custom hostname being used)

; <<>> DiG 9.10.6 <<>> shop.deco.cx
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19425
;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;shop.deco.cx. IN A

;; ANSWER SECTION:
shop.deco.cx. 300 IN CNAME sites-decoshop.decocdn.com.
sites-decoshop.decocdn.com. 300 IN A 104.18.10.25
sites-decoshop.decocdn.com. 300 IN A 104.18.11.25

;; Query time: 269 msec
;; SERVER: 2804:29b8:1000:1::17#53(2804:29b8:1000:1::17)
;; WHEN: Mon Dec 04 15:42:39 -03 2023
;; MSG SIZE rcvd: 113