Sanyo PLV-Z2 prefers fan in high speed lately

Stays in high speed all the time!

My apologies if this is documented, widely known, etc. but my PLV-Z2 (bought very early on, still with version 1.0 firmware) has very recently (last 2 weeks or so) started being evidently permanently in high speed fan mode. I believe there are two speeds, normal and high speed, and somehow mine has decided to do high speed constantly. I just turned it on and it was in low speed about a second or two and switched to high speed. The room is cool (lower 60s), and I cleaned the filter only a week or so ago (the original notoriouly porous filter that gives rise to dust balls very readily, although for some reason I haven't noticed any dust balls displayed on the screen for quite a while). On its original lamp, this PJ hasn't been used a hell of a lot, maybe 3000 hours. What could be the matter?

I'm the only person who has touched this PJ or touched the remote. Maybe I accidentally switched it, but have no idea how that could have happened. I don't even know how to switch it. AFAIK, the Z2 defaults to slow fan, not high. In the past it only went into high when the room was at least somewhat warm and the thing had been on a loooooooong time.

Hmmm... I bet I did hit the lamp mode button by mistake. Next time it goes on (probably tonight), I'll hit that button and see if it calms down. I am pretty sure that's what happened. I really am hardly into the settings of this thing. Figuring out the remote drove me nuts early on and I've never wrestled with it since.