Phone Bluetooth connection playing up

recently my Bluetooth on my OnePlus 7t can't hold connection with certain devices. For example when I connect my phone to my hi FI system after a few seconds it will cut out, and it does the same for a mobile speaker. Other phones work fine with these devices. So I thought, Bluetooth must just be knackered on my phone, but I can connect to my laptop and even my headphones normally, no problems. This started a few weeks ago, and I don't get any major updates anymore. I've done the basics, restarted my phone, reset Bluetooth and WiFi settings, forgot the device. But I really don't get why it will hold connection normally with only certain devices ? I've had my phones now for a few years.