Was upgrading from 1.21.9. Failed with an error. Reinstalled 1.21.9, good. Installed 1.21.10-60.0.5, also good. Error is [17:35:50] [main/ERROR] [ne.mi.fm.lo.mo.ModDiscoverer/SCAN]: Locator net.minecra ftforge.fml.loading.moddiscovery.ClasspathLocator@7dc51783 found an invalid mod file net.minecraftforge.fml.loading.moddiscovery.ModFileInfo@4b61d0c6 net.minecraftforge.fml.loading.moddiscovery.InvalidModFileException: Illegal version number specified ${forge_version} (forge-1.21.10-60.0.6-universal.jar) I can add more info if needed but I'm guessing this was just a whoops.