Just started today. Is this normally a symptom of the broken handle casting or the plastic cam on the inside broken? The key will lock and unlock with difficulty on the unlock.

Probably just the door cam. They are weak and are basically a "fuse". In other words you will want to lubricate it mechanism as it make it slide easily. If it takes too much force the plastic is designed to bend. I made mine so they can slide on easily (note the tapered pin).

-Mark
https://914rubber.com/door-cam-actuator-1-1

Best value is the cams with seals for both. It also includes the rings to replace the nylon ones in the lock assembly as the disintegrate with pressure and grease. The aluminum ones will last a lifetime.

https://914rubber.com/door-handle-repair-kit-1-4281

It is possible the latch has broken, there are some budget fixes for that too.

Door handle repair kit is a smoking deal

Autopsy

Often the lock/latch mechanism is very stiff and needs to be loosened up. I have found removal and saturating the mechanism in PB will get things working properly. I let the PB drain off for a day or so and then use oil to lubricate, not grease.