Why my croissant dough are always having butter going out during folding
Having some butter squidge out is par for the course. 
However, if this is more than can be folded back in (I've seen beautiful croissants from mis-shapen dough) then the question is: was your butter pliable or brittle? Brittle so that chunks fall out like ice sheets?

More pliable butter is achieved by adding 10% it's weight in flour (lower gluten variety).

Also 30min chilling is optimistic. Doable with a blast chiller and very cold tray. The whole 'tourieren' of 4X was done over several hours at my apprenticeship bakery. The later folds rested longer and longer.

Th final roll out for cutting too benefits from being relaxed enough to get a larger triangle cut that doesn't immediately shrink back.