Asus BE7200 FTP to server on VLAN?

[docfiddle]

I have set up a VLAN guest network on an Asus BE7200 router using its Guest Network Pro, isolated from main network per the "intranet access" setting (uncheck intranet access: Main Network). The guest SSID is propagating through an AIMesh network of nodes (2 AC3100, an AX1800S, and an AC68U all with the latest firmware.) Because a wireless Reolink E1 camera on the VLAN guest network (ID: 53) can no longer FTP recordings to a wired main network NAS, a QNAP 251B running QTS 5.2.6.3229, I configured a USB wireless dongle on the QNAP to be in the same VLAN (IP, subnet, VLAN tag) as the camera.

The wireless adapter shows up in the Guest Network client listing on the router.

QNAP FTP settings in QuFTP:
Port 21
Unencrypted FTP
Service Binding not enabled — all adapters should be listening on port 21.
I have confirmed that credentials on the camera and the NAS are the same and correct.

Reolink Cameras all have the same FTP login and RW settings except the target IP. Wired cameras FTP successfully through the #1 QNAP main network adapter; the wireless camera is on the guest VLAN and points to wireless dongle adapter IP.

Findings:

• The camera still fails to connect to the FTP server, with error 454: connection failed.
• Recordings from wired PoE cameras on the main network FTP normally to the NAS at the its #1 wired adapter IP.
• The NAS notification app and FTP access log shows no login failures or even attempts to login by the camera. It’s as if the packets never leave the camera or just never arrive at NAS.

Is there a way to configure the router to let FTP services pass through to devices on the same VLAN?

I've also posted a query to the QNAP forum to confirm the correct settings for the NAS.