It's not a bug. Having multiple XML objects w/ identical names has become an error in BfA.
Ideally, embeddable libraries shouldn't create/define anything in XML because it's impossible to update such objects. But due to oUF's nature, we have to use XML templates because there's no way to do what we need in Lua.
The only solution to your problem is to disabled embedded oUF in both addons, and to use standalone version of oUF for them.
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