Update #1:
Thanks for reaching out to the Miro Support team.
I understand that you noticed an issue with unlocking groups of grouped widgets, and I'm here to help!
I was able to reproduce the issue you reported and have shared it with our engineering team for further investigation.
I'll keep you updated as soon as I hear back from them!
As per the support team, this is expected behaviour based on an architectural limitation.
The explanation:
When you lock a group in Miro, it creates a new group that is locked. Widgets themselves do not support locking; only groups do. Therefore, when you lock existing groups, a new group is created that overwrites the original groups and becomes locked. Once the lock is disabled, the new group unlocks, but the original groups are no longer present.