BI can control PTZ with WAN address but not LAN address

[aesterling]

Hello, I have an Amcrest ASH21 camera on my wifi network that I've added to BI. The video stream works fine but BI cannot control the pan/tilt of the camera when using the local IP address. However, if I edit the camera's IP address in BI to my external WAN address and momentarily port-forwarded ports 80 and 554 to the camera, then BI can control pan/tilt. When I change it back to the LAN address, it cannot.

Any idea why PTZ control doesn't work with the local IP or how to troubleshoot?

I'm using Google Wifi as my router in a very simple configuration. No VLANs, no access/parental controls enabled, and no other settings that I'm aware of that would block communication between local devices. The BI PC has two network cards installed.
I used the PortQry command-line tool on the BI PC to test the status of those two ports on the camera using both the internal and external IP addresses. The results were the same: LISTENING.

For what it's worth, BI can control other PTZ cameras using the same ports on the same wifi network without a problem.

Thanks in advance for any suggestions.