B737 First Officer reported a flap asymmetry problem on approach. The Flight Crew executed a go-around and complied with the Checklist/QRH procedures. The Flight Crew then flew the approach to landing at destination airport.

Narrative

I was PM during base leg of visual approach (XL via channel). Landing checklist had been completed at Flaps 15 per company SOP. PF called for F25; PM selected F25 and then noticed trailing edge flap asymmetry (L flap 15; R flap 25) on the flap comparator. PM alerted PF to asymmetry and visual approach was terminated and crew requested a turn and climb away from the airport to conduct checklist/QRH (Quick Reference Handbook) items. No rolling moment was felt by the PF once the AP was disengaged. QRH items completed and landing was uneventful. Flaps were left down for maintenance inspection upon taxi back to ramp. Contributing factors are many. One being the company's decision to continue to operate aging aircraft well past their prime. Second being a general hesitancy amongst the pilot group to report safety/aircraft reliability concerns due to fear of the operational impact. I have witnessed numerous mechanical discrepancies get passed to maintenance verbally vice being written in the logbook. This should not be tolerated as it does not allow a history of discrepancies for a particular mechanical issue to be documented which can impact troubleshooting. This ultimately impacts reliability and aircraft availability.