hi friend, here in Italy we don't have that model, but from the problem as you described it it would seem you need to replace the revolver chuck parts..
which can no longer grasp the cap, the parts codes I don't know, but I send you an attachment of the mp2501 (just to make you understand what I mean),
then maybe they are the same, I don't know.
item 1 bottle chuck
item 9 slider assy.
best regards
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