Bluetooth connectivity with Yamaha A/V receiver disrupted after update to ios 12.3

My IPhone 8 Plus and my spouse's IPhone 7 which were both recently updated to ios 12.3 refuse to connect via bluetooth to my Yamaha A/V receiver. Both these phones use to connect flawlessly before the ios update. As a proof of the problem, my IPad which I didn't update to ios 12.3 connects just fine. Has Apple removed compatibility with certain Yamaha devices in ios 12.3 ? Please can someone help me with this as it is very annoying.