Can't enforce the "minimum equilateral edge length" criteria in block
 

My block has T-Rex on one of the domains and spherical sources very near to the domain. T-Rex delta is 4, and sources have a constant spacing of 5. Although I enforce a minimum equilateral edge length of 5 for tetrahedra and pyramid cells (I know that T-Rex layers are not affected by this), there are always a few cells within the source regions with edge lengths smaller than 5 (down to 0.9). Further refinement and smoothing operations won't fix this. I couldn't find another option/operation to guarantee this constraint. Can you please advise? Thanks.