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.
Dave Klish, I recently bought a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.