BOTHans

Hey, I have a very annoying issue that my world in the modpack rlcraft keeps crashing. Whenever I join the world my game stops responding so all I can do is close it how ever sometimes it just kicks me out and says "Invalid move player packet received" and sends me to the multiplayer server list. This happend after I allmost killed a dragon but before I could finish it it disapears which happens a lot about 2 of 10 dragons disapear. After the dragon disapeard I summond my flying mount and went on it and then it crashed. Since I get send back to the server list I dont get a crash report and even in the folder for the modpack under "crash report" nothing got added pls help