I want to chime in as well regarding this issue. I am also having issues with my wireless charging since updating my Galaxy S6 to Marshmallow. I have never had issues using my Galaxy wireless charger until I updated my phone a few days ago. Since then, it will behave as if it's charging, but it is actuality not. The Battery statistics show that it's still on battery, even though it's placed on the wireless charging station. I've restarted the phone several times and have power cycled the wireless charger to see if that would help but it has not.
Clearly, there is an issue with the Marshmallow update that is preventing the wireless charging from working properly and needs to be investigated.