regioncalc5 = ToElementMesh[regioncalc4, MeshRefinementFunction -> ff]
TetGenTetrahedralize: Tetrahedralize returned an error, 2.
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The TetGen manual at http://wias-berlin.de/software/tetgen/1.5/doc/manual/manual.pdf states for error code 2 (see appendix):
message: Please report this bug to Hang.Si@wias-berlin.de. Include the message above, your input data set, and the exact command line you used to run this program, thank you.
description: This failure was caused by a known bug of TetGen.
So I am tempted to think that nobody but the TetGen developers can help you.