Most Jobs Disappear on Matrix Plugin Upgrade

[Dan]

Jenkins version: 1.609.3 Long-Term Support Release

Matrix Project Plugin: version 1.4

Every time I upgrade the Matrix Project plug-in (to version 1.6), all but a couple of my ~2 dozen jobs disappear.  This has been the case for probably a year or so, and I keep hoping one of these upgrades will fix it.  I generally upgrade the other plug-ins with each Jenkins update.

What is the easiest way to fix or at least diagnose this?

I'm guessing there is some plug-in dependency that is causing problems...