I use contentBlocks with Repeater elements and TinyMCE. As soon as I move an element, the view in TinyMCE switches to source code view. The TinyMCE controls also disappear.
MODX 3.2.0
ContentBlocks 1.15.0-rc2
TinyMCE Rich Text Editor 3.1.6
This looks like a bug to me. As ContentBlocks is not an open-source extra, maybe try the dedicated modmore forum or see if you can contact Mark directly.