Aligning multiple exposures

I’m mostly using a Minolta X300 for multi-exposures work.

My process is as follows:

1. I make sure the camera’s crank is winded;

2. I insert the film into the cylinder making sure the cylinder doesn’t move, and make a pen marking of how deep into the cylinder
   the film is pushed;

3. I feel with my thumb where camera’s gate is and push to make a marking on each side with my nail or a marker;

4. At the end of the first pass and exposing all the photos, I rewind almost completely and repeat through step one.

This process has brought 90% chance of success, but sometimes for a reason I don’t understand, there are 3-4 millimeters of the photos that do not perfectly overlap.

What can I do to better align the exposures of each pass?