This worked fine up until a couple of days ago. The symptoms are: Flash never fires for correct exposure in (M)anual mode or TTL mode. Flash will fire a preflash for exposure adjustment, but will never actually contribute to the scene. Flash fires at full power in Auto mode ("A" on the flash). Never does anything else. Always full power, all the time. No flash compensation settings, either on the flash unit itself, camera exposure compensation in P mode, the SCP TTL exposure adjustment for the scene, or in the command panel for individual flash groups (enable SCP, "OK", "Info"), have any effect on these results. Always no contribution in M or TTL, always full power in Auto TTL. Things that have been tried so far: Mounting the flash directly on the hot-shoe of both my E-P5 and E-PM2, and used RC mode. A, S, M, P modes on the camera. Setting flash exposure compensation to both linked and de-linked from sensor exposure compensation (in utility menu F). Using the flash unit's own menus to select between Auto ("A"), TTL Auto, M, different focal lengths, manually setting flash power by GN or by fractions. Rotating the flash unit around to face the command flash (LM2 on the E-PM2, onboard popup unit on the E-P5). Placing a piece of exposed film over the master flash to make sure that only the command signals, and not the preflashes for control, are contributing to measured exposure. Cleaning the sensor glass/pip on the front of the FL-600R. Can anyone think of anything else to try? I mean, at this point I'm pretty sure it's buggered, but if there's anything else..