Firstly, apologies for the delay in responding here and any inconvenience this issue may have caused.
I checked with internal team on this to confirm few things around your issue.
You mentioned on the issue as “ failover fails because a health probe port on the new primary is in use by some other application, such as a monitoring agent.”
So you can try using a different port, or try to figure out which other application(s) are interfering with the Load Balancer resource.
I guess this is NOT a problem with WSFC, which works for many other customers who are running on-premises and some other clouds. This could be some issue specially you are seeing in your Azure Environment. This has to be checked by Network Support team (I would recommend you to open a support case).
Internal team has confirmed that the WSFC’s DNN resource would work well in the SQL Server Listener – so the Load Balancer does not need to be used at all Ref: Configure DNN listener for availability group - SQL Server on Azure VMs
Hope that helps.
If you need further help on this, tag me in a comment.
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