As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INFLIGHT BOTH LT AND RT EFFIS DISPLAYS FLICKERED ON AND OFF. AT ONE POINT UNABLE TO NAVIGATE. LT PITOT HEAT FAILED. AIR RETURN TO BNA. COULD NOT DUPLICATE. REMOVED AND REPLACED NR 2 DPU AS PRECAUTION ON ON 622-7713-004. S/N ON 4767, S/N OFF 6667. NR 2 DPU/EFIS SYS. OPS CHECK GOOD IAW SF340 MM CHAPTER 34.