bug in tinymc
Using Jamroom
There is a new Javascript loader that was created for Jamroom Core 6.4.1b5 and newer (also in Jamroom Core 6.5.0b1) that is designed to "bust" Chrome's aggressive caching which should avoid the issues that were seen in Core 6.4.0 when it was released with the update to TinyMCE 5, so this has been fixed.