The base cup is certainly the most problematic feature of the cannon.
Base cup too tight = O-ring is damaged.
Base cup falls off = O-ring is broken.
Pepper cannons are manufactured with very tight tolerances, so any variation in the size or condition of the O-ring can be noticeable.
Giving the base cup a twist when removing/replacing will extend the life of the O-ring and a touch of oil helps if it's tight. O-rings are friction parts that will wear over time.
5 extra O-rings are included in the box with each new pepper/salt cannon and you can get extras here:
https://mannkitchen.com/products/replacement-o-rings-for-pepper-salt-cannons-5-pack
Or, if you have another source the size you want is 35mm OD x 1.5mm.
So, why keep using the o-ring as an intentional design choice?
I've tested quite a few:
Threaded bases clog. The threads (we tested multiple types) make the base cup cumbersome to remove/replace.
Magnetic bases increase shipping/duty costs and always require two hands to remove the cup.
Ball dents require two hands to remove the base cup, and springs deteriorate.
I’ve stuck with the o-ring solution since it's the most versatile. Users that want the base cup to stay on can have that, and others (like myself) can remove the o-ring and use the cup as a base.
I find it easier to just be able to pick up my cannons with one hand and immediately begin seasoning, then put it back on the base with zero mess.
Hope this helps!
-Cleve