I think the emerging consensus
is pretty clear.
- There is something wrong with the unit.
- It would be fascinating to at least some of us to figure out the root cause, or at least the "proximate cause" of the heating, but...
- It needs to be repaired or replaced (the former if there's a warranty, almost certainly the latter if not).
This being said, the one - arguably - loose end, from my perspective*, is whether or not the tweeter would get hot if no signal is fed to it.
I am not sure it's worth testing this and exposing the unit to an opportunity to suffer even more damage, but it
might (???) be a good idea to determine that the problem does indeed isolate to the active speaker unit itself, and not to something "upstream" of it.
__________
* and per this question from the
@mateematy