There is currently no official "fix" for Eaglercraft because a fully functional, official version of Eaglercraft for 1.20 does not yet exist. Most "1.20" projects found online are either feature ports (modded 1.8.8 versions) or highly unstable community experiments Current State of Eaglercraft 1.20.1 Official Development: The lead developer, , primarily maintains EaglercraftX 1.8.8 , which remains the most stable version. Community "Ports":

Eaglercraft 1.2.0 (based on Minecraft 1.8.8) introduced: