From AIBN:
During approach to Kittilä (EFKT) in Finland on 26 December 2012, LN-DYM, a Boeing 737-800 NG on Norwegian Air Shuttle's (NAS') air service NAX5630 from Helsinki airport (EFHK), came close to stalling. The outcome of a stall would most likely have been catastrophic, primarily because the elevator system at that time did not function normally. The elevator system worked only at a ratio of 1:250.
AIBN's investigation has uncovered that de-icing fluid had ingressed the tail section and frozen on three or four of the input cranks for the aircraft's two elevator Power Control Units (PCUs) and thus prevented them from functioning as intended.
More,
Report on the serious aircraft incident during approach to Kittilä airport in Finland (EFKT) on 26. December 2012 with a Boeing 737-800, LN-DYM, operated by Norwegian Air Shuttle ASA | aibn