With most machine guns theres a number of things that can go wrong heres what the manual say:
"Should Jams occur in firing this may generally be attributed to the defective management of the drum"

It goes in to some detail in a couple of sections about how to operate the drum correctly to avoid problems and how to clear jams from other causes and it also has instruction on how to go about removing the locks, I think though most remedies other the simple jams would take way to much time in combat and present a serious danger if the enemy was close and advancing rapidly....

The Handbook Gatling .45 calibre Naval British version:

https://archive.org/details/handbookforinch00offigoog

If you want more technical info on the guns themselves this American manual may be helpful it also includes images of just about everything associated with the guns:

http://www.forgottenweapons.com/wp-content/uploads/manuals/Gattling%20Gun%20Caliber%2045.pdf

The British manual is only one I've seen of several that includes the info regarding jamming etc

Too put it in perspective normal rate of fire for a gatling gun is 525rpm this is equivalent to about 50 men rapid firing with Martini Henrys, but the barrels would quickly get to hot to handle.. the gatling could however maintain that fire reliably for up to 8 minutes non stop with a good crew before ammo started cooking of in the barrels.....