2 cents more. I have had this problem several times and have learned a trick to solve the problem. This assumes that the collet itself is not faulty.
Any more, I never put the router bit in the collet so that it *bottoms* all the way into the collet. This allows me to tap the router bit on the working end along the axis that drives the bit further into the collet. This makes a space for the bit to move in the collet toward the router. When the bit moves toward the router it always *releases* and I can get the bit out of the collet easily because the bit has a mm or 2 of space to move- Or more if the bit does not need to be in the collet deeply.
Of course always tap the router bit on the end and with something that will not damage the bit.
My solution will not work if I put so far that it has no room to move toward the router. Then I have had toresort to prayer and a bigger hammer, duct tape, WD40, block and tackle, multiple pipe wrenches, dent pullers, and a great deal of sweat.
Hope you get the bit out soon.