I had this problem today in exploration mode, when I got to the first orbital mission.
1. I was using the same craft that earlier I had full gimbal control of.
2. I checked that I was using the correct engine, I was using the Swivel, not the Reliant.
3. I removed the engine, saved the workspace, then put the Swivel engine back on and resaved.
4. I double checked gimbal settings by right clicking the part, everything was enabled.
5. I double checked SAS/RCS settings, everything was normal.
6. Still no WASD control.
7. Reloaded the save, Still no WASD control.
8. Reloaded the game, WASD control returned.
