If it is working when you are using a different file manager - it is not the system itself - but you have narrowed it down to Thunar.
There has been various topics over the years relating to Thunar, I don’t recall any of those to be related to removable devices though.
I am assuming your system is up-to-date - implying a regular run of pacman -Syu.
Also assuming the package gvfs is available.
For the nfs mount see [root tip] [How To] systemd mount unit samples and the parent topic [root tip] [How To] Use systemd to mount ANY device