It's an old problem that I'd hoped had been fixed by now, but it's still here:

ex.:
/set %test %test2
/set %test2 proof-of-concept
Here %test2 will return "proof-of-concept"

Now I can reset %test2 by forcing an evaluation in a script:
/set [ [ %test ] ] success
And from now on %test2 will return "success"

HOWEVER:
Should I want to delete %test2 this way it will fail:
/unset [ [ %test ] ] will not unset %test2, it will ignore the forced evaluation and unset %test instead.

The bug is reproducible and has been encountered by me frequently.
Is it a known problem ?