Using WWAN and WiFi simultaneously

I have a Windows 10 Tablet that has a WWAN 4G Modem and a WiFi adapter. The WiFi adapter is used to talk to another local computer (not coected to the inteet), and the 4G Modem is used to talk to the inteet. Independently, they work great. However, when they are both tued on at the same time and coected to their respective network/device, only one of them has a priority over the other at any given time that I caot seem to find a way to control. So either the WWAN works and I can access the inteet but am not able to talk to the other computer over WiFi (ping/ftp), or when the WiFi has the priority I can ping/ftp into the local computer, but am not able to access the inteet with the WWAN. I tried tuing off Automatic Metric from the Network Adapter Settings and set the Interface Metric with a higher number for one adapter and a lower for another, and then switched them, but it seems that the WWAN has the priority both times.

Note: I discoected from the WiFi Network and used an Etheet cable to coect this tablet to the local computer just as a test, and everything was working fine (without any changes to the Interface Metrics).