This is a known issue. DELLEMC have recalled BIOS 2.14.0 on specific platforms. The issue apparently relates to a microcode update in the 2.14 release not playing well with Intel E5-26xx v4 CPUs. There is apparently a replacement BIOS on the way that will correct the issue. In the meantime the current mitigation is to roll back to 2.13 which you seem to have already performed.