Intermittent Bluetooth after Rear Case repair

So I recently did a screen and rear case replacement on my iPhone 6s plus, and ever since, my bluetooth has been cutting in and out, at times completely disconnecting from my watch and speakers, and when it is connected, it cuts in and out, making it impossible to listen to music.

The replacement rear case came with multiple parts already installed, including the buttons, wifi.bluetooth antenna, cellular antenna, and lighting/headphone assembly. (photo of old casing included for reference) (wifi/bluetooth antenna missing as already replaced part)

I have replaced the wifi/bluetooth antenna with the original that came with my phone to minimal, if any, improvement.

Is there anything else I can replace on the that might be the issue?

I maybe thought about replacing the wifi diversity cable with the original incase that was the issue, but didn’t know if this affected bluetooth performance and don’t want to completely dismantle my phone again to replace one cable that may be pointless replacing.

So my question basically comes down to;

• Does the wifi diversity cable also handle bluetooth diversity?
• If not, what else can I try replacing to get my bluetooth working again?