There are several threats about this issue, see https://forums.ubports.com/topic/457/the-bluetooth-thread/18 and the files on github (e.g. https://github.com/ubports/ubuntu-touch/issues/766)

My phone is a bq Aquaris E5HD ubuntu edition and now loaded with UBports image. My car is a Citroen C4 Picasso with the MyWay system from Harman. The version of this system is rneg_D_R50b_R50.03. That should be the newest one.

The behaviour is like this:

First when the two sides dont now eachother and starting the connection/ coupling from the car, all is working. It is possible to make calls and to see the addressbook of the phone.

After this when trying again the connection is not made anymore.
The phone says that the car is connected, but the car says the phone is coupled, but not connected and connection is not possible.

Yes I did. But I don't know how. It's long time ago... Recently I had the same issue again and the cause was the wrong phone no.

No, the port is not abandoned. The Xx is now a community device with devel channel and gets updates.GPS is working fine.

I had the same issue a time ago. For me it helped to delete all parts via UTTT.

Thank you also @fredldotme. That sounds great. I'm very eager.

@fredldotme I have the result of the command. I sent you an e-mail.

Ok, I have the device and can try that command. I think first I have to install UT on it, right?

Today I've got a F5122 and I would love to see it with UT. But I think I don't have the capability to make it happen.

On https://github.com/Halium/projectmanagement/issues/98 you can find:

xsetiadi asked on 21 Aug
does this will work too for xperia x dual? F5122? @fredldotme

fredldotme commented on 21 Aug
In theory yes, practically I don't have the device available. But since I modified the source in a way that's not specific to F5121 it should work just fine.
The only area I could see issues with is ofono needing an override to support the second SIM tray.

On XDA I found this thread: https://forum.xda-developers.com/crossdevice-dev/sony/universal-sony-dualsim-patcher-t3930983 Perhaps a solution for the dual sim issue?