KC868-D16 all tested light bulbs are flickering

[stansvec]

I tested four classic tungsten incandescent light bulbs and four halogen lights (8 in total - please see the picture). All of them flickered on almost all brightness levels. Is this unusual or unexpected? If so, what could the problem be?

1. Could the dimmer unit be faulty?
2. Is a 24W power adapter enough?

The lights are connected to three separate SSR relays, so assuming these are okay.