I flooded the battery compartment of an Ikelite S51 I once had. Charged the batteries the night before and they were still hot when I took them out of the charger. So I put them in the strobe but only loosely tightened the compartment cover meaning to tighten it fully the next morning before diving. Guess what?
In respect to Inon battery cover O rings, I found with my S2000s using less grease was an improvement together with using the palm of my hand rather than my fingers helped in screwing on the cap evenly and not catching the O ring.