Yea I am not sure what variable is too large, but I am running it just fine on the RTAX88U with no variable issues. And other users run it just fine on other model routers running asuswrt merlin firmware. It is hard to say what could be the cause. It actually sounds like there may be an issue with the firmware specific to that router. That doesn't sound normal at all. I imagine on earlier firmware versions you were not having this issue correct? I remember you mentioning you just started having these problems.
Here are some troubleshooting steps:
Try passing the
sh -x argument when running the installer. It is possible NVRAM is corrupt or hanging.
Maybe the USB storage (or Entware) you are using has gone corrupt. You could try installing with a new USB storage.
Maybe you are experiencing side effects or "bugs" that were not previously noticed in your current firmware version.
Maybe your router is running out of memory in your NVRAM or JFFS (you would need to do a factory reset and purge your NVRAM).
All of these issues are external causes which could be producing undesired consequencies for which I cannot determine myself since I am not experiencing this concern. You would have to conduct an Audit of your setup. Determine no external factor are the cause, and then I will try to troubleshoot on my end. As of right now I am chasing an issue I cannot reproduce myself.
Also, if you are using amtm to access the installer , you could try using the terminal download command instead. (This is incase you have a bady copy of the installer or are having issues with amtm.)
Code:
curl -L -s -k -O https://raw.githubusercontent.com/jumpsmm7/Asuswrt-Merlin-AdGuardHome-Installer/master/installer && sh installer