The problem is similar to this: https://forums.spiralknights.com/en/node/113413
It occurs not on my pc but on someone's I do play with, so I don't have all the specs, but what I remember is: (will update later)
-Asus Laptop
-Win10
-7th generation Core i7
-12 Ram
-2VRam/ Nvidia GeForce 900 series m/mx
-1920 x 1080 recommended resolution
Latest Java is installed and copied over into the game files replacing the old java_vm folder, as it is in my own pc.