Stabilizing Old Door

This door has sentimental value otherwise I wouldn't bother. It is a 32x80 paneled door with a large 23x40 lite. I believe it's white pine. The whole door is loose. I can grab hold of the knob and shift the thing. The problem could have started when I was dumb enough to trim it to size by ripping only the top and exposing the mortise and tenon.
I thought of applying the stuff to the joints that swells the wood. I used it on some chair stretchers once but they loosened back up after a year. I also considered squaring it up, and drilling and doweling the joints. It's a funky door and if I sanded and stained the dowels I wouldn't be bothered by the appearance. I should add that it was an interior door but now it opens to an unheated porch in a cold climate area. It's 1 3/4 inches thick.
Any other suggestion would be appreciated. I guess if I had to, I think it might be loose enough to take apart and reglue.
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