OK, let's forget about High/Normal for a while and focus on the particular options of the Standard Shield provider.
Please, open the resident protection control window (on computer
A), select "Details" (if it's not chosen already), select the Standard Shield provider and press "Customize" button (it doesn't matter if the level is set to "High" or "Normal") and go to the second page of the settings.
So, do you say that if you set exactly the same options as shown on the left image, it will freeze when you access the disk of this computer from the other one - and if you set the options displayed on the right image (i.e. you turn off the "Scan created/modified files" option) - it will work correctly?
It's rather strange... because even with the setting on the left image,
no extensions are selected to be scanned... so the behavior should be the same