The L11_calc_celerity subroutine in mo_mrm_net_startup uses a variable slope_tmp which has been declared but not allocated. This is not an issue normally as slope_tmp is given values and deallocated at the end. However, when number of nodes is 1, slope_tmp is not given any values and mhm throws error at deallocation.
Thanks to Prabhat Banjara (Institute of Engineering, Nepal) for finding out the bug where one of his domain was small enough to be included in a single mhm pixel, leading to this error.