This is probably going to sound a bit ham fisted but it work's if you are careful enough.
1 pairs of small pliers.
1 soft cloth. Maybe microfiber.
Open the clasp & using the cloth as a buffer put it on one end and with a little pressure widen the end out a fraction.
Try the fit and if all's well job done.
If it's still a little tight repeat on the other side. Until you get a good balance between locking tight and ease of opening.
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