I'm assuming you're not pounding it in with a hammer. I can't see a little snugness having anything to do with it. Timing it against a watch for a minute or two wouldn't reveal much unless it was really, really off. WiFi wouldn't have any effect either.

Woodcraft's site appears to be down at the moment so I can't look at their offerings but does the clock have any way to regulate (adjust) how fast it runs? There may be a slot or small screw with a +/- symbol near it?

Very odd. These clocks are based on counting oscillations of a crystal and even the cheapest should be good to 10-15 seconds a month. They can vary a bit with temperature, is your sunporch extremely hot? Maybe they got a miscalibrated batch of clocks, you might buy a movement from another source and try it--they run about $6 on Amazon, so it's not an expensive experiment.

Yep, neither hammering nor baking the clock. On the back it says "No (0) jewels. Unadjusted." I don't see anything on the back that looks like someplace to adjust. There is a tiny screw, but it doesn't have any marks near it, and I think it just holds the plastic cover on the back. But I just went on Woodcraft's site (why didn't I think of that?) and one of the people who commented said he bought one that lost time every day, and the other guy got a defective one, too. So it looks like maybe this is more common than I thought. I was trying to support my local brick and mortar, but maybe I should return this and find a different brand from someone else. Thanks for your help!

try Klockit

Thanks, sloyder, I will check it out.