I am sorry, but once you are at BIOS 367, you simply cannot downgrade. This is because changes were made in the Management Engine firmware in BIOS 367 to mitigate the INTEL-SA-00086 security vulnerabilities (for more information, see here: INTEL-SA-00086 Advisory). Now, once a security update is made to the Management Engine firmware, it will not allow downgrades to any previous version. This is a design feature of the Management Engine that simply cannot be circumvented. I am sorry, but you will just have to wait for a new BIOS update to be made available.
The BIOS was withdrawn because of instabilities in the microcode updates made for the SpectreB vulnerability (for more information, see here: Facts about The New Security Research Findings and Intel Products and here: INTEL-SA-00088 Advisory). Unfortunately, this instability manifested worst in the microcode for the Haswell (4th generation Core) and Broadwell (5th generation Core) processors. You have already encountered and described it's instabilities fairly well.
Since the BIOS withdrawal was done, Intel has root-caused the microcode issue, made the appropriate changes to the various microcode releases and is in the process of validating these changes. Once the validation is complete (and presuming it is satisfactory), the microcode will be released to board manufacturers. They, in turn, will be responsible for including the appropriate microcode releases into their product BIOSs and releasing them to their customers. Intel's NUC team will be similarly responsible for doing this for the NUC products and also for the older Intel Desktop Board products. They will publish their schedules for delivery of the various BIOS updates to these locations:
Unfortunately, these schedules cannot be set until the microcode is made available (that's why they are blank right now). All I can say is, watch these sites for schedule updates.
I wish I had a better answer, but it is what it is. Don't shoot the messenger; I am retired and a volunteer here.
I'am still waiting for a BIOS update which makes my NUC usable as it was bevor I prematurely updated it to 368 which was withdrawn short later again.
Also I downgraded to 367 the performance is still awful and the issues already described in my inital post persist!
This is not acceptable! I want my NUC back as it was with BIOS 365: Stable, fast and usable!
Not going to happen for a while I am afraid. Keep watching this page: INTEL-SA-00088 Schedule for Intel NUC, Compute Stick and Compute Card. Eventually, you will see a schedule for the delivery of a BIOS update.
Whining doesn't help,
This message was posted on behalf of Intel Corporation
Downgrading to BIOS 367 should have removed the microcode update.
Would you mind checking your registry to see what microcode is being loaded?
The key is HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0.
Please provide a screenshot of the subkeys. We need to see the Update Revision and the Previous Update Revision.