Sensor Classic - Lights go out, then come back

Hi folks, been having a weird issue that i suspect might be one of my Sensor Classic racks that controls the house lights in my venue.... This occurs when the lights in that rack have been off for a period of time, and then are brought  back up to full. The lights will go out for a second, then come back up. The first time I really noticed was when a guest LD had taken control of my system from a GrandMA2 via sACN, to an ETC 4-port gateway (firmware version I was able to recreate the issue multiple times, both from own console (Eos Ti v3.1.3 b8) via Net3 through the same gateway, and my DMXcat (bypassing the gateway). I have also noticed the same thing happening when I take control of the house lights from our Unison wall stations. I haven't had a chance yet to watch the dimmer rack at the time the issue occurs.

Has anyone experienced something like this before? Any thoughts on what else I might be able to check or look for? The dimmer racks here are 25 years old, so I suppose it's not out of the realm of possibility that the control electronics are starting to fail just from age.

Thanks in advance for your help!