Docker not releasing memory when shutdown, windows 10

I have recently started using docker for new development work, however I am still required to switch back to working on our older on-premise offering from time to time. That is, I sometimes need to shutdown docker and spin up a an installation of our on premise server.

I find that when I do this with docker installed the performance of this server is terrible, essentially unusable, I need to uninstall docker to get it to work again.

When I have docker running I can see it using the memory (my machine has 32 GB of RAM, I am telling docker to use 16) and when I shutdown docker I can see it being released, according to the task manager anyway, and I can also see on hyper-v manager that the VM has been shutdown. However the performance of on-premise server install continues to act as the memory is in use. This is not a small performance hit, actions that should take 1 second take 20 or 30.

It would seem like docker is not actually releasing the memory on shutdown and only does so when I actually uninstall it, when I do this performance recovers completely.

Is this a known issue? Is there anything else I can try to see where the memory is going? I can find no other reports about it.

I am using windows 10 with docker version 17.03.1-ce-win5 (10743)