Try to run HUU and select update all instead of selecting only BIOS.
As per Cisco documentation,
"Always upgrade the BIOS, the Cisco IMC and CMC from the HUU ISO. Do not upgrade individual components (only BIOS or only Cisco IMC), since this could lead to unexpected behavior. If you choose to upgrade BIOS, and the Cisco IMC individually and not from the HUU ISO, make sure to upgrade both Cisco IMC, and BIOS to the same container release. If the BIOS and the Cisco IMC versions are from different container releases, it could result in unexpected behavior. Cisco recommends that you use the Update All option from the Host Upgrade Utility to update the firmware versions of Cisco IMC, BIOS, and all other server components (VIC, RAID Controllers, PCI devices, and LOM) together. "
https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/release/notes/b_UCS_C-Series_RN_4_0_2.html
