To be done “right,” — it should really be disassembled entirely, the PCB’s sent through a proper ultrasonic solvent bath, followed by a bake out (+85c should do), then a repeat dip and final bake-out before it’s put back in service. And those wires/cable harnesses should all be replaced. They’re junk now. You’re never getting the contaminants out without a vacuum chamber.
Isopropyl is hygroscopic — meaning it’s able to carry water away with it (in addition to salt). Water, well, isn’t. RO/DI is going to remain in the light, and contaminants are going to pool around component leads, under parts, and in tight spaces — which is exactly where we DON’T want them to collect since those areas are prone to shorts to begin with just due to physical proximity of active metal.
I assumed OP doesn’t have the same level of experience and comfort with PCB level electronics as a 25+ year elecronics tech-turned-EE so I suggested a method of cleaning that should be “good enough” without pushing OP too close to the “oh crap, I broke my expensive light for good” point.
Honestly, if it were me, I’d buy a replacement, send this one in for refurb, and either keep it as a backup or sell the extra once it returns. But that’s an expensive proposition, and still not entirely off the table if a quick fix attempt doesn’t work.
