I sometimes mill my own lumber from windfall on my property - in the first instance somehow I managed to put a single piece of near green lumber (~40% moisture) in the same rack as some lumber I knew was dry.

A few weeks later I needed some scrap for something, grabbed the piece closest on hand, pushed it into the blade and immediately triggered the wet wood alert and the blade spun down slowly. I knew that the wood wasn't wet, so started the saw up again and pushed it straight back into the blade only with more force, triggering it straight away.

Second time was due to cutting a lot of pitch heavy pine over an extended period of time - it built up on the cartridge and after a blade change that I didn't check the clearance on, it bridged the brake with the blade (i assume) and triggered on start up. (It comes with a tool to check this clearance after a blade change - I of course did not follow the instructions).

I've triggered one by touching the blade too soon after it has stopped. There is a short delay between when the blade stops and when the brake is disabled. I've also had one trigger on a heavy miter through some gnarled 8/4 walnut.