Previously shower smelled damp, even if ventilation was good. Reason: cracked tiles, cracked grouting and broken shower trap what lead to growth of mould, unpleasant smell and became damp the ceiling under bath (lower level).
All plasterboard wall was wet behind tiles and was removed, damp insulation removed and replaced, wood studs were dried over few days with dehumidifier, mould treatment applied to woodwork, new insulation installed properly to reduce pipe condensation and noise cancellation, new plasterboard installed, damp proofed, homelux damp seal applied all around shower tray to prevent further water leakage behind tray, re-tiled the walls, shower tray trap replaced with new, old door cleaned and reused, applied extra mould and water protection over tiles, all corners and around shower doors sealed with silicone.