Just saw this when reading this thread. Running Cura 4.8, and my printer is an Ender 3 Pro, with Marlin 220.127.116.11. Installed the Cura plugin for Arc Welder (ver. 3.5.0) and all ran beautifully...great curves!!! Upgraded to 3.5.1 and everything went to hell. Extruder starts by laying down a HUGE amount of material before simply going bonkers. I manually rolled the Arc Welder plugin back, resliced and all is well again. Unsure what I can provide to determine what happened between 3.5.0 and 3.5.1 in the plugin world.