Error EDDDAV: Call to ZHEGV failed

Davidson algorithm has failed... solve with other IALGO? other mixing factors? Minor change in positions has appeared to solve it as well, despite the original not being too unreasonable.

If the calculation restarts from a previous CHGCAR, it sometimes helps to delete that CHGCAR (i.e. restarting the SCF cycle from scratch).

Finally, there might be something wrong with some VASP compilations. The problem sometimes disappears when changing the parallellization settings (e.g. the calculation might fail in parallel, but work on 1 core, or with a different KPAR). Observations of issues with raising KPAR and lowering ENCUT could also point to issues with swapping.