react-dnd HTML5 backend from react-mosaic can conflict with other non-Mirador components

[broadwell]

This is perhaps best addressed via a note in the wiki, unless an in-code fix is much easier than expected. The gist is that if Mirador 3 in Mosaic mode is embedded in another React app that uses react-dnd in a different component, the two can produce the dreaded Cannot have two HTM5 backends at the same time error. This can happen even when toggling from Mirador 3 to the other component, due to the asynchronous tear-down behavior in React 16.

This comment succinctly captures the problem, the challenges react-dnd's architecture poses to an in-code fix, and the easiest workaround:
facebook/react#11106 (comment)
The workaround is to set a state flag in one of the components so that it doesn't render until mounted.