OBC_REDUCED_PHYSICS
The OBC_REDUCED_PHYSICS option is selected by default when TIDES is enabled but UV_TIDES is not. This situation (define TIDES, undef UV_TIDES) occurs when we nest simulations within simulations that already contain TIDES and only keep the tidal potential on. However, OBC_REDUCED_PHYSICS should not be used in this case (it is very unstable).
# ifdef TIDES
# ifndef UV_TIDES
# define OBC_REDUCED_PHYSICS
# endif
# endif
Solution: Remove the "define OBC_REDUCED_PHYSICS" from the cppdefs.h