Garage door opener works sporadically

I have an Allister ARD 11A garage door opener, about '88 or '89(?) vintage that works sporadically. In fact, it doesn't work more than it works. But basically, sometimes it works, sometimes it doesn't. It may open, then not close, or it may work a few times, then not work, etc.
There is both a remote and a wall switch to activate the door. The problem has nothing to do with the remote, as when the door does not work, it won't work either way.
I spent awhile playing with it today, and found a few things out.
There are 3 relays on the unit, and when I manually activate them by pushing on them, they work fine. I can push one, and the door goes up. I push another the door goes down. The third is for the light. So, the relays are fine.
When it does not work, the appropriate relay is not getting activated.
Maybe I'm on drugs, but it seems like it barely works in the summer with hot, humid weather.
What can make the door work so sporadically?
Having the door work has become more important lately because I just got a new convertible that is going to displace all the sports equipment that is in the garage now. ;-)
Thanks.
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You might just want to replace it... they are pretty darn cheap these days.

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Not really on topic...but I remember seeing a report a while back that I wanted to ask about. Some reporters drove around a neighborhood with garage door openers and found they were able to open many people's garages from the street, without coming onto anyone's driveway. Apparently many GDO's were operating on the same frequency. This WAS a while back, but I was wondering...can people still do this?
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