AsyncPrimitives | Async concurrency primitives for .NET | Reactive Programming library

This only applies to Visual Studio 2022. I had uninstalled VS2019 and Preview where F# worked absolutely fine (F# 5.0). I am using VS2022 to use F# 6.0 and do not want to go back to F# 5.0.

The issue is specific to F#. I also use C# and I have no issues running the latest C# under VS2022.

There are near continual DevEnv processes running consuming anywhere from 1 to 4 of my CPU's 4 Hyperthreads. I have switched off all experimental options I can find in F# settings.

Sometimes there are 2 or more background processes running , sometimes paused and sometimes none - there appears to be no correlation between this and the background CPU consumption

Sometimes I have a pop up Dialog about waiting to complete an editor process or a compile process.

When devenev.exe is consuming CPU cycles under the properties I see there is always one clr.dllCoUnInitializeEE+0x6790 that is the culprit. I though this was meant to be a short-lived process? Sometimes there are two or three of these consuming most of a HyperThread (There are identical others but with very low or no CPU consumption). The stack on the guilty thread is as follows:

Here is a minimal sample that will reproduce the issue.

Trying to hit that endpoint, either with a Fable client or just navigating to http://127.0.0.1:8080/ITestAPI/Test causes the server to throw a Method not found: