I don't quite understand if this is a confliction with another mod or something else, but just a few minutes ago on a creative world when I put a Rusty Ladder in my hand, first the singleplayer server crashed, then the client. I will put the crash report in here if anyone wants to take a look at it.

Note that yes, I use a cracked client, but that's becuse I'm broke. Drill into me about the cracked client if you must. Also if you want to know what cracked launcher I use, it's called SkaiaCraft Launcher 2.0.
crash-2019-04-28_10.00.31-client.txt