The copy_to_zone function in GLM does not process diagnostics.
https://github.com/AquaticEcoDynamics/GLM/blob/f83530eaf476c16a34cbd21d827dcd8d6d0de858/src/glm_aed.F90#L1022
This is an issue for simulations with benthic_mode=2 where diagnostics are required to be used in calculations
(Note that the FV-AED version of this function includes cc_diag and works properly.)