M4L device that works in Max not working properly in Live

I have a M4L device that seems to work in Max but, when I close Max, it doesn't work right in Live.

For example part of the device updates a number box based on buttons pushed on a Launchpad. This works perfectly, every time, when the device is running in Max. I close Max and sometimes it works, sometimes it gives spurious results.

It's the same device so I'm kind of puzzled. Has anyone seen this kind of thing happen before? Any ideas what may cause such problem?

Matt