If you hold the tablet with the cover (ie the display side) down, the strength of the magnetic closure is no longer enough to keep the cover securely. In my measurement of magnetic opens at approx 190g weight. If you move the Tablet, but affects more than just the weight, so my idea for the magnets should hold at least 300g.
On my Samsung Galaxy Tab 10.5 S (2014), the automatic switch off of the tablet when closing the cover does not always work; the Auto. Turning when opening works, unfortunately not.
Do you have to apply a trick (eg in the tablet settings)? I have found nothing, and fear that there is no remedy. I'm curious, how magically the signal is transmitted from the shell to the tablet. Probably here lies the cause of the malfunction.
I would have more reliability when closing and switching on / off is desired, ie, on whose behalf I had (low price and moderate weight) decided at the Kandidatenendauswahl just for this product at the product features.