@IndyMike,

Thanks so very much for the verification. #648.

With kind regards,
Michel

I replaced one of the misbehaving KPLs with a factory-fresh one -- happens to be a v.44.  (I used the existing scene and the utility in ISY that replaces an existing device with another one.  There were no communications glitches in the process. )  I checked that the Device link table is identical to ISY.  With Link type default as installed by 5.0.14 it behaved the same as the old one.  Changing the link type to Insteon with any number of retries did not affect the situation.  The key is that somehow the ISY thinks that the load (A button) is On 100% when in fact the load is off and the A button light is also off. 

Oddly, I just changed the load link type back to default (on the C button screen) and the behavior has improved somewhat -- the load now does respond to the C button control of the scene but with a delay -- as if the clean-up message is working after the direct load control fails.  I had seen this behavior some with the v.43 KPL also but can't be sure why it did this sometimes and other times not.  As always, the load responds synchronously with other loads when the scene is commanded from a different KPL or from ISY.    [It may be that the improved behavior had to do with a sequence of turning the load on and off and then commanding the scene and not changing the link type -- I can't be sure].  

Here is some of the event log and the scene as reported for the C button.  The KPL in question is 39.7A.8B.