I discovered this same error on another one of my sites with a different set of plugin conflicts. The really strange thing is that this one is working with The Events Calendar v4.2 and The Events Calendar PRO v4.2 installed and activated however does not work with SearchWP v2.6 active.
For this site, the error is appearing on an ACF option page. This particular option page only has 2 fields as shown here: https://cloudup.com/c17oDtvAqNT. With the js error: https://cloudup.com/cuXmYGVQjBa the date select field does not display any selectable dates. For now I’ve downgraded from ACF v5.3.9.1 to v5.3.8.1 as a workaround.
