A simple scenario:

1. I have a windows host (with discs C and D) with configured just one regular item key "vfs.fs.size[C:,pfree]" which is working.
2. I've linked a new 2.0.0 template "Template OS Windows" to the host (one discovery rule (60 seconds update interval), one item prototype, one trigger prototype).
3. I got additional lld-item (for disc D) and two lld-triggers (for discs C and D).

But I got the lld-trigger for disc C, which belongs to the regular item, which was existed before.
It's NOT very good, I consider this as a bug.

An error status of the discovery rule is always "Cannot create item [vfs.fs.size[C:,pfree]]: item already exists"

Expected server behavior, IMO: server should not create lld-triggers for such regular-items.

Frontend issues then:
After "unlink and clear" the template, lld-triggers (wrongly linked to regular items) will stay (with flag=4 in DB) but visually they look like regular triggers.

When I try to open such trigger by just click (these is a link already as for a regular trigger) I receive an error:
ERROR: No permissions to referred object or it does not exist!

Luckily it's possible delete such incorrect triggers using checkboxes and a drop-down delete action.

p.s. this issue created after investigation in ZBX-5713