There may be other similar situations, perhaps with both the Selector & Multiplexer, but I find this frustrating, a CPU waste, & repeatable:
1) Drop a fresh Selector in the schematic
2) Connect a Float into the second input
3) The Selector goes into "Float-mode" as it should; all good
4) Connect the output to a Float, no problem
5) Connect the output to a Poly
6) The entire Selector enters "poly-mode" where all connectors become Poly (bug #1), using more CPU (since it is not in green-mode now), & preventing the Selector's out to connect to any more Floats (bug #1.1)
7) Disconnecting the single Poly connection will not revert the Selector back into float-mode, even if all the in & out connections are Floats, but it is now stuck in Poly-mode! (bug #2)
Same issue with other green connectors later connecting to any Poly/Mono/Pack4/Stream(needs the connected item to be coerced)(/Double?).
edit: Bug #3: The change from green to audio is so stuck, even undo will not undo the change. It will stay in that audio mode though several [Ctrl-z]s!
Workaround: Connect the Selector's out to an empty pass-though module before connecting to any Stream. Costs like 1Kb, but saves frustration & CPU I think.