Issues on Mixed Mirrors of IRIS vs. Caché

I'd like to make you aware of a trap I just fell into.

I run a Mirror for Caché some while using an Arbiter - OK

Now some  months later I installed IRIS and planned a Mirror with ISCAgent:

That broke my ISCAgent for Caché.
And in addition to my Caché modules my analysis showed me:

On Windows, ISCAgent is installed into C:\Program Files (x86)\Common Files\InterSystems\Agent\

And in added to my Caché modules, I see a bunch of iris*.dll and CacheCOM64.dll nicely side by side with IRISCOM64.dll.  
BUT: only 1 ISCAgent.exe with a fresh date that isn't interested in Caché at all. Replaced by the install.

Once identified after some research this was fixed rather fast by a correct version.
and working it after I found this important note in Locating the Arbiter to Optimize Mirror Availability which applies also to IRIS

Be aware of that trap.