I've just started getting this error in Azure Devops pipelines using the MS hosted agent. I have made no code changes, it just started happening.
Error LGHT0091: Duplicate symbol 'Property:WIX_IS_NETFRAMEWORK_472_OR_LATER_INSTALLED' found. This typically means that an Id is duplicated. Check to make sure all your identifiers of a given type (File, Component, Feature) are unique.
After some investigation (comparing raw logs in the pipelines) my working builds a few days ago were using Wix3.11 but looking at the logs for the failed pipelines they're using Wix3.14.
Looking in GitHub for the runners, there has indeed been a change (happened early March 2024) to mitigate a vulnerability. See https://github.com/actions/runner-images/issues/9426 so Wix3.14 is now the minimum version to use.