Magazine feed issues
AFAIK, most Mauser-based designs used a staggered arrangement for cartridges in the internal box magazine, and this has led to occasional problems with feed reliability.
It's related to the shoulder angle, overall cartridge length, etc. and the feed lip geometry. As this is part of the action, it's kind of important to get it right the first time when a gunsmith is adjusting it.
When they work, they tend to work great and they stay that way forever.
External magazines can get bent, have a locking mechanism that can be difficult to release or difficult to engage. They can use a staggered arangement and feed from alternate sides, like an internal box magazine, or they can feed to a tapered "centerline feed" design, or they can just plain be an in-line magazine.
These can also be great and stay that way forever, provided the magazines don't get bent up in rough handling. (Very unlikely in typical civilian service.)