There are some spots on the tab when covered stops transmission of Bluetooth and wifi, not sure why it is, experimented with covering antennas on other devices, there doesn't seem to be a problem.
As per your query, We request you kindly visit the service center for a physical inspection of your device. So that they can check the exact issue with the device and fix it at the earliest. You can locate your nearest service center with this given link: https://www.samsung.com/in/support/service-center/
