When updating a "discovery" trigger prototype on the Linux OS template, I have the following problem

Incorrect item key "hostname:vfs.fs.size[{#FSNAME},pfree]" provided for trigger expression.
Cannot implode expression "{hostname:vfs.fs.size[{#FSNAME},pfree].last(0)}<{$CRIT_DISK_FREE}". [CTriggerPrototype.update -> CTriggerGeneral.inherit -> CTriggerGeneral.inheritOnHost -> CTriggerPrototype.createReal]

When I go and look at the "hostname" trigger configuration, I see 2 auto discovery rules (FS and NET) but they have 0 items/triggers/graphs (while they should have multiple items and triggers)

As a workaround, I have to re-link the Linux Template, which unfortunately causes the loss of all the data I have for those hosts.

Is there a way to force a re-association of the templates without losing data?

Regards
Alessandro