Thinking about this... if you've got the other cup out you could use the plumbers freeze stuff and spray the stuck cup with it - hopefully it'll contract and with some injudicious brute force you might get it free?
@andyp started
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Thinking about this... if you've got the other cup out you could use the plumbers freeze stuff and spray the stuck cup with it - hopefully it'll contract and with some injudicious brute force you might get it free?