Hi,
It seems as though the keyboard is losing its connection at that point of its' travel range.
Have you tried detaching and then reattaching the keyboard to see if the problem is then still evident?
If it is still evident after trying this, how long have you had the laptop? The manufacturer has a 12 month warranty on the device. If your tablet is still covered by the warranty period, consult the warranty statement that is in the documentation that came with the laptop as to what you have to do to make a claim for a warranty repair or replacement.
If you cannot find the documentation, search online for Microsoft Surface Book warranty in your location.
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