I have 3 switches, 2 are HS210 and one is HS200.  They have been installed and working for months.  Yesterday one of the HS210 started blicking the lights continuously.  This morning a second HS210 and an HS200 also started all blicking the lights continuously.   Each are controling different lights.

I have shut power off to the light switches.  If I restore power all three now immediately start blicking the lights.

Presumably, each is wired correctly since they have all been working without issue for months.

Any advise on what would cause this?  And how do I fix it?