Hi Milenin welcome to W7F
Until you can find a test keyboard try going to:
Control Panel\All Control Panel Items\Ease of Access Center\Make the keyboard easier to use
Scroll down and if Filter Keys is ticked, un-tick it.
Then click on Set Up Filter Keys
If Turn on filter keys is ticked un-tick it.
If turn on filter keys when right-shift is pressed for longer than 8 seconds is ticked un-tick it.
Click on apply for any changes you make, then click okay when done.
If you do make changes see if your new settings help. Strange Shift Key Behavior (Microsoft Word)
You do not have to have MS Word installed for this behavior to occur.