you can try talcing the edges of the button-- basically trying to reduce friction.
a longer-term fix requires a complete disassembly of the aleph, which is annoying. basically the mounting of the circuit board (which holds the key switches) needs to be pushed slightly in the opposite direction of where the buttons are jammed. this is a somewhat fiddly process of tightening screws at the right moment and rechecking the key alignment/operation.
of course i’d be happy to do this for you-- but likely not worth the international shipping costs.