I have HS220 smart dimmer installed and at infrequent random times, the lights will dim for a brief second then return to normal brightness. It's like the lights dip for a second. It occurs at any brightness setting including 100%. While infrequent, it does happened a few times every evening. 
we have several other non-dimming smart switches and those do not have the same issue. 
 

any advice would be appreciated.