During the Pie beta on the S9 we voiced several complaints to Samsung, one being the weak cell signal and another a wifi problem. On my S9 and now the S10 if I move out of my 5Ghz range wifi will drop to 2.4GHz. When I'm back in range of 5Ghz the phone stays locked to 2.4GHz until I cycle wifi on and off. I have a wifi mesh system and I'm almost always in range of 5Ghz unless I'm in the yard.