The under-seat harnesses are pretty robust (at least from looking at the W124 and R129 units with the seats removed), so unless you have standing water or an unusual kink or sharp object severing the wires and exposing them, I wouldn't consider that area.

Are your seat switches on the seats or on the door panels? If on the door panels, I would look there first. The switch harness is a bit thinner in that area, and if the wires got pinched after a recent door panel removal and possibly the window mechanism intrusion, then that might be the place to look...

...also, the fuse blowing w/o the operation of the seat switch has me perplexed. What other accessories share that fuse? Perhaps it's not the seat at all?

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car