Using Unity's Default Third Person Controller causes jerky air control.

I'm working on creating a platformer game where the player is capable of stringing jumps together in order to create a higher jump. Using Unity's Default Third Person Controller, however, I've noticed that the character has extremely jerky movement in the air, oftentimes barely moving at all. The character will stop and start repeatedly while in the air.

This occurs with the basic controller without any modifications, but since the default jump is so small it's not noticeable, but it's very noticeable and debilitating to play when the jumps get higher.

Does anyone know why this occurs, or how to fix it? I think it might be a lag issue, but to be honest I'm very much a beginner and don't fully understand why this is occurring.