Morning Michael, ignore my comment from last night, a fresh morning and I think I've cracked it using cfMesh. I only left the solver to run for 4 minutes but it was error free through that time. I ended up modelling a quadrant and then using Draft Polar Array all in FC 0.19.4 it fully meshes at 1.8mm element size. I'll make a more detailed step-by-step later today but find the attached file to try. I have to say this is quite unusual to give such hassle from the modelling side of things but the quadrant technique isn't silly when you're looking to use the smallest amount of geometry in the sketches, the master sketch maybe over the top in this instance but it's really good practice for when the user looks to have really complex models as they progress.
OS: Windows 7 Version 6.1 (Build 7601: SP 1)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24267 +148 (Git)
Build type: Release
Branch: Branch_0.19.4
Hash: 476ecf091941bead59b14e44afa6064d5a66afa3
Python version: 3.8.6+
Qt version: 5.15.2
Coin version: 4.0.1
OCC version: 7.5.3
Locale: English/United Kingdom (en_GB)