Well, the image looks very good and detailed, albeit bright for my tastes.
I'm surprised you were shooting 180 second subs. Mine 'blow out' at a much less exposure.
In fact, I've been fiddling around at 1.5 to 3 second subs with the Infinity OSC.
I did get very brave the other day, and took the back off my Infinity to look for any sign of desiccant tablets. None found.
But I admittedly did not dig deep. Just the back and stared into the PC board. (And there certainly was nothing to write home about.)
But I'm not about to dig any deeper. Nor remove anything else like the lens retainer.
At any rate, I wouldn't kick your 383L OSC out of bed for eating crackers. The image looks great to me.
If I lived next door, I'd show you how to do a vacuum drying of the camera. Opening up the desiccant chambers, and putting the camera in a suitable chamber, like a wide mouthed Mason jar. Then use a vacuum sealer to do a dry vacuum sealing on the jar.
We do vacuum treatment on refrigeration systems. And one time we were vacuum treating electrical coils for contactors and relays when a power plant got flooded.
We had a large Bell Jar vacuum chamber. I'd put the coils in it and pull a vacuum on them. Any moisture boils off under a vacuum at normal temperatures. And that dried out the coils enough to past testing so they could be returned to service.
Vacuum treatment of large power transformers to dry them, and the insulating oil, was a fairly routine service when testing shown it was due.
Anyway, at least you have desiccant tablets to work with.