Slow to non extant upload with a AX12 Rax120 connected to a d7000v2 in modem only (bridge mode)

Hi,

I have an AX12 RAX120 connected via ethernet to a d7000v2 in modem only mode. Download works absolutly fine; however upload is slow. I also have an office that is a long way from the house and connected via ethernet to a netgear in access point mode. With other routers the upload and download speed is fast and fine in the study. Hwever with the RAX120 acting as a router I get normal download and 0.0 upload!!!

A similar situation occures with my Orbi mesh in  the house - works fine with other routers but 0 upload with the RAX120.

It gets stranger still. On some speed test tools the upload is normal, e.g. PC and mac using speed test applications. If I measure speed with google speed test however I get 0 upload again on my mac.

It means that many devices do not work properly e.g. firestick, appletv or my wok laptop.

Does anyone have any idea what would cause this behaviour?

Many thanks in advance for suggestions.