A57 wifi speed drops to 20 mbps

I'm currently using a TP Link Deco M4 wifi mesh on my home. I have this problem on my phone (Samsung A57) where it drops from 300 mbps to 20 mbps. It seems like it starts to drop when I roam around. I've checked everything on the Deco app and my phone's connected to the 5 GHz band and it still drops to 20 mbps. My other devices doesn't have this issue. I've tried almost everything, from turning on and off fast roaming to tweaking different settings on my phone. Does anyone have the same problem? What could be the problem?