i've seen it go on by itself after hitting some small bumps.
It could be the short in the circuit you mention, but start by completely eliminating the easiest choices first. Check all the fuses in the fuse box - the older metal oxidizes and develops hairline cracks that can cause the fuse to work intermittently. Check ALL the bulbs in their sockets to make sure they have good connection, good filaments, and clean contacts (use care in removing bulbs - one of the forum members got a finger full of glass when installing a bulb). A loose bulb, dirty contact, or a marginal filament can cause a work/fail pattern.
Really hope that it isn't an electrical short - my flickering/failing right brake light was eventually traced to an exposed section of cigarette lighter power wire!
It can take a fair amount of time to find and fix, as it could be on a seemingly distantly related circuit or a ground connection wire!
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
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