SqlClient: Microsoft.Data.SQLClient throws exception trying to access Azure SQL Database

I am running two .NET6 apps on Linux Azure Web App containers, which need connections to a Azure SQL database. The first one connects to the DB without problem, the second one, deployed on the same service plan with the same configuration, throws the following generic exception:

 Unhandled exception. Microsoft.Data.SqlClient.SqlException (0x80131904): A connection was successfully established with the server, but then an error occurred during the login process. (provider: TCP Provider, error: 35 - An internal exception was caught)
  ---> System.IO.IOException: Unable to write data to the transport connection: Connection reset by peer.
  ---> System.Net.Sockets.SocketException (104): Connection reset by peer
    at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 count)
    --- End of inner exception stack trace ---
    at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 count)
    at System.IO.Stream.Write(ReadOnlySpan`1 buffer)
    at System.Net.Sockets.NetworkStream.Write(ReadOnlySpan`1 buffer)
    at Microsoft.Data.SqlClient.SNI.SslOverTdsStream.Write(ReadOnlySpan`1 buffer)
    at Microsoft.Data.SqlClient.SNI.SslOverTdsStream.Write(Byte[] buffer, Int32 offset, Int32 count)
    at System.Net.Security.SslStream.WriteSingleChunk[TIOAdapter](TIOAdapter writeAdapter, ReadOnlyMemory`1 buffer)
    at System.Net.Security.SslStream.WriteAsyncInternal[TIOAdapter](TIOAdapter writeAdapter, ReadOnlyMemory`1 buffer)
    at System.Net.Security.SslStream.Write(Byte[] buffer, Int32 offset, Int32 count)
    at Microsoft.Data.SqlClient.SNI.SNIPacket.WriteToStream(Stream stream)
    at Microsoft.Data.SqlClient.SNI.SNITCPHandle.Send(SNIPacket packet)
    at Microsoft.Data.ProviderBase.DbConnectionPool.CheckPoolBlockingPeriod(Exception e)
    at Microsoft.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
    at Microsoft.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
    at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
    at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
    at Microsoft.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
    at Microsoft.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
    at Microsoft.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
    at Microsoft.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry, SqlConnectionOverrides overrides)
    at Microsoft.Data.SqlClient.SqlConnection.Open(SqlConnectionOverrides overrides)
    at Microsoft.Data.SqlClient.SqlConnection.Open()
    at BBB.Identity.Configuration.IdentityServerConfigurationProvider.Load() in D:\a\1\s\BBB.Identity\Configuration\IdentityServerConfigurationProvider.cs:line 26
    at Microsoft.Extensions.Configuration.ConfigurationRoot..ctor(IList`1 providers)
    at Microsoft.Extensions.Configuration.ConfigurationBuilder.Build()
    at BBB.Identity.Configuration.IdentityServerConfigurationManager.SetIdentityConfigurationRoot() in D:\a\1\s\BBB.Identity\Configuration\IdentityServerConfigurationManager.cs:line 34
    at BBB.Identity.Configuration.IdentityServerConfigurationManager.InitializeIdentityServerConfiguration() in D:\a\1\s\BBB.Identity\Configuration\IdentityServerConfigurationManager.cs:line 17
    at Program.<Main>$(String[] args) in D:\a\1\s\BBB.Identity\Program.cs:line 15

To reproduce

Not sure how to provide reproducibility as it is a private project. I myself can’t reproduce the issue somewhere else: When deploying the app locally and connecting it to the Azure SQL db it works.

Expected behavior

A working connection to the Azure SQL database.

Further technical details

Microsoft.Data.SqlClient version: 4.1.0 .NET target: .NET6(.0.301) SQL Server version: Azure SQL database Operating system: Azure App Service Plan Linux

Both apps are on the same service plan, have the same connection string, the same configuration and the same software versions. I can not imagine where the difference lies, which could produce the connection error.