Lights on 4-Way Z-Wave Switches are Flashing

Hi there.

I have had my ISY994i with around 30 Insteon devices for around 10 years now, and it has generally been working very well aside from the occasional Insteon switch failure.

I have had a few such failures lately, and, given that there seem to be no new Insteon devices to be had, I have been slowly subbing in Z-Wave replacements.  I got my Z-wave controller around 4 or 5 years ago to control a Schlage deadbolt, and I cannot seem to see my Z-Wave devices with any ISY firmware past 5.0.16C, so I assume that I have the older board.

The Z-Wave devices have generally been working well, except for a 4-way installation of UltraPro (Jasco) switches (one master and 2 slaves).

The issue here is that occasionally, the lights controlled by these switches will flash when an Insteon device is operating.  This does not happen with another of these switches in a single pole installation or with either of the 2 Z-Wave outlets I have in the system, so I am assuming that the slaves communicate with the master over the neutral and somehow the Insteon signals are getting in there.

Has anyone else experienced this, and can anyone offer any thoughts on a remedy?

For reference, both ISY and UI Firmware are 5.0.16C.

Thanks so much!

RS