Greetings,
I'll try and research your issue more, but have to agree with support, that upgrading to the latest isn't always best. Hardware is not always created equally, so some BIOS revision will work, while others will not depending on hardware or other conditions. Overclocking, using non QVL RAM or forcing aggressive clock speeds, voltages or timings may not work in every situation either.
14 BIOS revs for this board. You CPU is supported from F20.
"Despite this , I have found users reporting successful upgrade with same RAM/ MOBO combination with older gen CPU ( ryzen 1st gen)"
Exactly, you aren't running a 1st gen CPU. So why is this relevant? Having a Summit Ridge CPU doesn't guarantee BIOS support past F25. What happens if you load defaults and run everything at stock speeds? Do revisions above F25 work now? If you aren't using QVL RAM, results are likely going to vary.
Similar example. My Z97 board. 4th Gen Devil's canyon CPU. BIOS F8 was last 4th gen release. Later BIOS revs added support for 5th gen Broadwell CPUs. Many people who upgraded to later BIOS revs, who were still running 4th gen CPUs had problems with stepping, and cores refusing dynamically downclock themselves when idle. This was all BIOS related in conjunction with the hardware being used with it.
You are welcome to continue experimenting.