I don't deal with pool lighting or pool control systems, but I've been asked by an existing client to help solve a problem their pool service company has not been able to address.

Short story: Pentair Intellights installed 3 years ago with no controller. The light colors/preset programs are selected by toggling a standard light switch on and off X number of times. The lights worked fine for a year or two and then some of the lights failed and had to be replaced. Since the replacement, toggling the common light switch causes the lights to land on different colors/programs. The client does not observe a constant offset in the color difference (i.e. The results are somewhat random).

According to Pentair docs and forum entries I've read, there is no command or control language to default, reset or synchronize the light engines. The Intellitouch controller merely automates the switch on/off sequences.

As such my theories thus far are:
1) The new and old Fixtures are of different hardware or firmware version
2) Whatever electrical event destroyed the lights that failed (if any) also damaged the light engines in the remaining original fixtures.
3) Corrosion/wear is causing arcing on the light switch contact which confuses some fixtures about number of on/off events.
4) Electrical noise/interference or neutral contamination are causing issues with the older fixtures--Pentair appears to have addressed some problem with electrical system noise via hardware revision around 2013, though this would not explain why the original fixtures operated normally for 2 years.

Any other considerations or experiences out there?

Here's what a Pentair Rep added to a forum string regarding a similar issue, though I do not understand how a filter cap would affect/improve the circuit's ability to receive discrete power on/off events:

"A filter capacitor has been implemented in early 2013 to resolve this issue is caused by site‐specific electrical noise. If your lights where manufactured before this point, this could very well be what needs to be corrected."