Devices cannot inter-connect between 2.4Ghz and 5Ghz band

Hi All,

I used my M2 MR2100 with the latest firmwire (NTGX24_10.13.09.00) to setup a small network in my car and there are a few devices connected to it including phones, laptops, a mobile NAS, a dashcam and my car.  Most devices connects to the 5GHz band while for dashcam and my car they connects to the 2.4GHz due to the lack of support.

All devices can connect to internet fine but I found the devices cannot be interconnect between the 2.4GHz band and 5GHz.

For example, I find that the dashcam (2.4GHz) cannot connect to my NAS (5GHz).  Same case my laptop (5GHz) cannot connect to my dashcam (2.4GHz).  Like ping / FTP they all fail.

They can interconnect if I uses 2 different SSIDs and forces all devices connects via the 2.4GHz.  Can do ping and FTP file transfer.   But it would slow down a lot for my other transfer like between my phones / laptop / NAS.

Is this a bug or something I missed out in the setup on MR2100?   Though I believe it is a very common feature as in a normal home router to support file transfer between 5GHz and 2.4GHz band.

Appreciate for any advice.  Thanks!