The hanging symptoms were as follows: No download from the internet. Still able to seen on RMS and green dot showing. Reboot not making any difference to this state.
Device used as the only internet connection in a domestic property, connected via sim card to 4G mobile network. The only setup changes from default were to use WAN as Lan to give 2 Lan ports. Also SSID & p-word were changed from default.
I have now remotely installed the latest version of the firmware using RMS. That installation process worked well.
The version I replaced was RUT2XX_R_00.01.13 which I still have in some customer devices. I'll upgrade those too.
Thanks.