I'm not sure what might be different, but my 4" membranes go in and out easily. Must be your adapter coupling from 4" slip (glue) to 4" female thread is somehow different, it should not be tight.
Once the membrane is in the storage tube, add a mixture of water with the right ratio of preservative in it and fill to the top, just below the threads, then store it upright in a cool dry place, I keep mine in the cellar.