So... I decided to grab an allen wrench and jump right in.
However, after removing the cranks and having a little trouble getting them exactly parallel with each other, I noticed that the teeth inside of the crank seem to be somewhat worn down. Is this normal? Or is this the reason they were slipping?
Photos - drive.google.com/drive/folders/1UWVtPWDkQOyqYxkyzAGdF32lALY7lngy?usp=sharing
Really appreciate any help!