@realpasscode 

Hi

It is recommended that you insert the same SIM card into your phone to share the hotspot Wi-Fi, and then connect other devices to the phone's hotspot Wi-Fi to connect to the VPN. Please verify whether the VPN in this case is stable.

In addition, please provide a screenshot of the Deco APP > Internet page and a screenshot of the APN settings page.
May I ask what VPN you have set up? Will there be any error message on the client when the VPN is disconnected?