Using the below mix, I've experienced this problem for several weeks, increasingly often.
Two days ago I ran the "Reinstall VMWare tools" option, and chose "Repair", and both the onboard and external keyboards have been rock solid ever since (as they have always been in OSX apps themselves). I may have missed it, but I haven't seen this recommended as a solution elsewhere. Hoping for continued stability.
MacBook Pro 2016 15"
OSX 10.13.6 (High Sierra)
VMWare Fusion 10.1.5 (10950653)
Hosting Windows 10 Pro