Hmm… strange that KDE behaves slowly in that thread due to a noauto mount, unless somehow it’s trying to auto-mount (e.g. autofs, gvfsd, or kio-extras ) a related NFS share or something. NFS is known to cause system hangs due to default blocking mounts, unless using the soft mount option (usually with: bg,intr,soft).
In any case, maybe the OP of this thread can review this KDE article about caches, and see if rebuilding the icon cache (?? command for this ?? 
), and the KDE SYstem COnfiguration CAche (e.g. kbuildsycoca5 --noincremental for .desktop and MIME type .xml caches)?