See what new BIOS settings for RAM Memory has changed.
Plus showing .1 gbyte less of RAM Memory isn't anything to worry about. It could, as you mentioned, a new BIOS setting causing the issue.
Open a Support ticket for your Motherboard since they are the ones the creates and updates their motherboard BIOS version and see what they say.
You can also open an Online AMD Service Request from here and ask them: https://www.amd.com/en/support/contact-email-form