i currently have this issue ongoing as well. the CCID tells me it's the left rear brake light assembly, but all bulbs are working fine, so i'm stumped.
'08 monaco blue E90 335i 6MT. sport pkg. premium pkg. black leatherette. brushed aluminum trim. M-Tech shift knob/boot. M3 mats. matte black kidneys. carbon performance trunk spoiler. blacklines. MTEC angel eyes. JB4. aFe stage 2 intake. custom downpipe-back stainless exhaust with 4" tips. mechunik plate mount. 19x9/19x10 +24 style 95's with 10mm BMS spacers in the rear.