Odd behavior from Ikelite strobe

I'm having a problem with my Ikelite DS-50 strobe that makes no sense,
and I'm hoping one of the wizards here might be able to explain it.

I'm using the DS-50 with the manual controller, which picks up the
deflected light from internal flash on my Canon A-620 in Ikelite
housing. What's supposed to happen is the controller picks up the light
and sends a signal to the strobe via a cable. The strobe then fires.
The controller contols the amount of flash the strobe emits based on
the setting I dial in. It works like TTL, and you're supposed to set
the DS-50 to TTL rather than manual.

When I set it up this way and test it dry it works perfectly.
Underwater, theTTL setting on the strobe does not work at all. To
operate the system underwater, I have to set the strobe to manual and
adjust the exposure entirely within the camera, set on manual. That
might not seem so bad, but I have a smaller range of exposure options
in the camera, and using the strobe on full manual means every flash is
full power, which considerably reduces battery time.

I sent the strobe back to Ikelite. They said they were unable to
reproduce the problem; in other words it seemed to work fine, according
to them. But it doesn't. I will contact them again, of course, but I
remain baffled about WHY a problem like this exists. There's no
leakage. If it were, it would affect the whole system, and it wouldn't
work again when dry. It's not a pressure issue, because it fails even
when barely submerged. What else would cause a failure like this
underwater when it works perfectly on the surface?

Any ideas?

Thanks,

gc