Mini-Menu broken in DEV

On my Surface Pro X (SQ2), the mini/context menu that is supposed to pop up automatically when text is highlighted no longer works.  It stopped working a few DEV versions ago, and is still not working.  I have tried reinstalling and toggling the feature (Accessibility -> Usability -> Show Mini Menu When Selecting Text), but to no avail.

Please help!  When using a pen, this is a very helpful feature to have.

P.S.  It still works on the stable build.