Weak Bluetooth Signal

Hi! I’m fairly new to the Banana Pi. I have a BPI-M2+. I set up retrorangepi on it. I paired my bluetooth controller with it (8bitdo NES30) and when I sat down on my couch it didn’t work, it didn’t input anything and after half a minute it disconnected. I reconnected it and it worked, but only very close to it (like 20cm), I guess the signal is really weak. Is it a hardware problem or a software one and is there any fix? Thanks for helping!