Client-serv. app run: System.ArgumentException: An item with the same key has already been added

Have an issue after deploying and running WebSharper client-server app to the remote server: I get System.ArgumentException: An item with the same key has already been added. Here is a gist with stack trace in my case . However all is OK on my machine while running with VS 2017 Community (F# 4.1, WebSharper 3.6.19.242, .NET 4.6). According to the info specified by hosting provider, their server supports ASP.NET 4.0, .NET <=4.6.3.

Still have no idea how to fix that. Can somebody help, please?

P.S.: Found very similar question/issue here (the last comment is mine).