Why is Chrome only using one core (2 threads) and how to fix it?

Question

Google Chrome

Google Chrome started to use only one core (2 threads) for work. Moreover, if you start the task manager and select it (Make the window active), then Chrome starts using all the cores, as expected. If you select Chrome again, or any other application (except the task manager), then again Chrome starts loading only one core.
If you enable the display mode "On top of all windows" in the task manager, then nothing changes - if it is selected - then Chrome works fine, if not - with one core.
In the manager settings for all Chrome processes, there is a similarity to all processor cores. If you manually set the affinity to only one (other) kernel, then these processes start using the selected kernels.
Before posting the question for a long time he tried to find a solution.
There are no viruses.
Chrome reinstalled several times.
Bios latest.
Drivers are fine, I also reinstalled.
Processor i7-4720HQ