Hi Robyn

I looked all over and I found something that related to a YouTube video dated back in 2012 the only other thing I found that sounded similar to your issue was with using the 3dconnexion mouse, Mojave and upgrading to Blender 2.8 and it seemed the person was having the same issue you are describing and the fix was uninstalling the mouse drivers and reinstalling them and that resolved their issue I do not know if this might resolve your issue since I have zero know how with Mojave I hope this helps some and I know there has to be someone else in here who works with Blender and Mac's

Lobo3433

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