It appears that Wordwitch has reached a decision (and I think correctly) after the conversation took a bunch of twists and turns.
Once again, there was all sorts of speculation at the start about what a "cram sandwich" could possibly be a misspelling of without seriously considering that "cram" could have been exactly what is right. A version of Occam's Razor was called for -- even if "cram sandwich" is an unusual expression.
I'd say that Jalapeño moved things in an appropriate direction in that this is another way of saying "cram it" (similar to "stuff it"). While there are other connotations to the phrase, some of which can be vulgar (Cram it/stuff it/shove it up your a**!), they are all basically a way of saying that someone should shut up.
From M-W, which considers only the "standard" meanings of "cram," but which shows the direction it can be taken:
Definition of cram
(Entry 1 of 4)
1 : to pack tight : jam
cram a suitcase with clothes
a novel crammed with surprises
2a : to fill with food to satiety : stuff
b : to eat voraciously : bolt
the child crams her food
3 : to thrust in or as if in a rough or forceful manner
crammed the letters into his pocket
4 : to prepare hastily for an examination
cram the students for the test
1 : to eat greedily or to satiety : stuff
2 : to study a subject intensively especially for an imminent examination
Definition of cram (Entry 2 of 4)
1 : a compressed multitude or crowd : crush
2 : last-minute study especially for an examination