In a run of pipes and structures, I have 3 structures that overflow. 2 of the structures max hgl els are even with the rim elevation (as is in the case of other runs in the same project), and 1 structure has the max hgl exceeding the elev of the rim. Why this one and not the others?
Check the structure settings for each. The one with the HGL exceeding the structure may be in sag and have a inlet ponding enabled. The others may be 'on grade' with no storage, and the overflow is simply lost unless you have a by-pass target set-up.