EC200T ipv4 not working when ipv6 is also enabled

I’m using EC200T module in USB ether mode connected via USB to an embedded Linux board. I’ve set the module in AT+QCFG=“ubsnet”,1 mode and when setup the APN for IPV4V6 and activate the PDP context using AT+QIACT=1, I’m able to ping both IPV4 and IPV6 addressed using AT+QPING.
However, from my Linux host, only IPV6 addresses are getting pinged, and for IPV4 there is no response. I can’t even ping the local IP assigned to the modem. (note: I’ve setup default gateway as the usb0 interface)
Another issue is with IPV6 DNS resolution. My Linux host is unable to resolve domain names to their IPV6 addresses, whereas autoconf is enabled for the usb0 interface.

You can see the known good configuration here: Port forwarding on Quectel EG912Y-EU - #6 by jfrog
This example is applicable to your modem as well.

If the problem persists, show the output of AT+CGPADDR, AT+CGDCONT? and AT+QICSGP=1 (assuming context 1 is in use).
Then on the Linux host collect the output of

ip a
ip r
ip l