So I'm knocking in a bat and cracks start appearing along the grain lines and I can feel these cracks, is this good or should I oil the bat again and continue a couple days later? (this is my first time knocking in a bat from scratch)
Give it a light sand, clean off all of the sanding dust then give it a light light oil. Leave overnight, then resume with the knocking.
Or just leave that bit until you've finished knocking in, the bat is going to crack up anyways, so I wouldn't worry too much about it until you've finished the job. Would probably recommend going a bit lighter with the mallet then building up the strike power. All depends on how bad and deep they are to be honest, I would probably knock in the surrounding areas to try level off the grains first before sanding!