ja, I'm having the same problem. I've been really good with OS 2-strokes, but converted to electric last year, or the year before? Anyway, took out my 120AX the other day and it quit on me a couple of times in flight. Amazing what a little time off can do for your ear/feel of an engine.

I'm sure you remember how to check the high end on the ground. My method for checking the idle mix is to run up engine on ground, drop to idle, and carefully watch the RPM. Should stay constant for a good 20 seconds, then start to drop. If RPM increases at all, especially in that 20 seconds, it's too lean.

How is the transition (idle to full power) on the ground? Hesitant, smooth, rough? If all seems good, may be the glow plug (can also be leak in fuel lines!).

My experience with bad glow plugs is that the engine just seems to quit for no reason - quits at any random attitude, not just climbs. Plugs are cheap and easy first solution.

Good luck,
Joe