Our experience has found that moisture was causing corrosion leading to the failure of the Bendix GCU.
Within the last three years, I've reviewed several aircraft maintenance records for various aircraft and noted missing entries regarding non-OEM-related equipment. It’s not the major maintenance and inspections that are missing from the logbooks, but rather the small unknown inspections and ongoing required programs that remain outstanding.
Although Service Bulletin SBF2-12-001 is not mandatory, API strongly recommends compliance during the next maintenance event in which the ailerons are removed from the aircraft.
If you have the centrifugal compressor impeller with the designated part and serial number, accomplish the initial borescope inspection at the next designated airframe inspection.