Hi @Martinski, OK, so I uninstalled YazDHCP and rebooted and input around 54 manual DHCP assignments by hand using the drop-down in the original (Merlin FW) DHCP assignments page.You could try running the same test scenario under the same or similar conditions using the native WebUI page (i.e. after uninstalling YazDHCP). If you experience the same problem, you could submit a bug report to ASUS, or perhaps @RMerlin might want to take a look.
I did it by hand (from a zero-entries start point) to reduce the chances of a wayward dhcp_list or custom_clientlist entry (and copying the wonky files to jffs/nvram/ which is what I had been doing in the past.
I did save these "clean" dhcp_list or custom_clientlist files to my desktop for future use.
The upshot is that the 6-field DHCP Windows all now come up just fine and populate fully, as do the 4-field ones. So this is fixed.
I am still not sure what caused it unfortunately, so it is hard for others that follow, with the same issue, to work it out, save to do what I have done,
So one step forward, but annoyingly what remains missing are the name entries in System Log, Wireless Log, an issue I detailed here, as this is a possible Merlin glitch (or user error, always a strong likelihood). Once this is fixed I will probably return to YazDHCP on the remote system, as saving, importing, editing, more DHCP assignments is just too good to miss. I have it running nicely on my local one.