I don't understand what it means for a knot to "jam."
"jam" mostly means "becomes un-untiable, stuck, 'welded'".
In more practical terms, it might not indicate
an all-so-problematic condition; it's esp. true
if the experienced loads are not so great.
Ashley's #1452 end-2-end joint has various
dressings, one of which can make it "jam"
--which can be "welded" under high loads,
but otherwise might be just the thing to tame
e.g. slick-springy polypropylene rope used
say for a dog leach.
Beyond this, one might want a "welded" tight
knot. Anglers, e.g., aren't in the business of
untying knots.
--dl*
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