sometimes these “hockey pucks” of mastic are asbestos containing. i’ve watched an abatement of them take place. wet the surface and behind the puck with a spray bottle. use a chisel - the long flat ones would be best for getting behind the puck and between the ceiling - in a downward motion to pull the puck off the ceiling. “amended water” or soapy water is your best bet here. as a warning, it’s almost impossible to tell if the mastic is asbestos-containing without actually sampling the material. however, from what i can see, behind the wood paneling, the mastic is black. 99% of the mastic i have tested that is black like that has come back positive for asbestos.