I use an AKG lavalier through one channel of my Zoom H6, and a Beyerdynamics mic/headset through another, with the Zoom H6 acting as pre-amp, into my H1. (Zoom H6 line out into H1 mic port.)
Three things I've picked up along the way. First, the quality of the cable linking the Zoom H6 to H1 is very important: I was using crappy cheap cables, which caused all sorts of problems. Bought a top-of-the range one - much improved. Second, take the gain on the H1's External Mic Level Adjustment setting as low as you can - I have mine on -27dB - and adjust the levels on your external pre-amp. Third, I was using OK quality ear buds to monitor the sound from the headphone jack on the H1's grip - very poor. But when I switched to a decent set of studio quality headphones, I found that I was, in fact, getting very good sound after all.
Remember also to turn Internal Mic Level Adjustment off.
End result, as I say, excellent quality sound and no lock-ups or any other problems.
FWIW, I have tried using the automatic setting and found it fairly useless.