Preventing ergonomic handlebar internal rubber cylinders to stick I have a bike with ergononomic handles (Fuxon brand).
Those are kept in position (as in prevented to rotate) with a mechanism which fits inside the handlebar.

This mechanism works by compressing two rubber cylinders along their axis, so they expand in the diameter.

Whenever I need to remove them for any reason (last time replacing the bar ends) it's a long battle. The rubber cylinders don't move even when the pressure is released. I risked many times ending with the rubber cylinders stuck inside the handlebar. Still, it takes no effort to push them in, but don't want this to happen again.

Any suggestion to prevent them to become stuck? Could I use some grease/lubricant, without making the situation worse or making them ineffective?

The current "solution" is to relieve pressure by unscrewing the thing, and wait. It took several weeks, until one day the thing came out by pulling.
Grease would make the rubber slip, defeating the purpose of the mechanism. And it might cause the rubber to deteriorate.

Best solution is to just throw these grips in the garbage, and get some better-designed ones. I've seen several types that use an external clamp (or two clamps) to hold the grip in place - I'm sure that would work better.

But if you're really set on keeping these grips, and don't mind getting "creative", you might be able to make an alternate locking mechanism. The expansion plugs that they use with carbon steering tubes would be ideal - except they're too big. So you want something that works on the same principle, but fits inside the handlebar. Go to the fastener section at a hardware store, and see if you can find expansion bolts that are the right size.