USB port data transfer not working

Kind of weird story, I have bought this used phone which looked like new, after about 3 days and some weird problems like signal loss it died. send it to warranty and instead of changing the phone they have offered repair and charged me money for it. anyway after repair I am able to charge the phone and fast charge is working but I don't have data connection. my friend is a mobile technician and he said he changed USB/daughter board and also reballed CPU and still it's not working but ye also said that data would work for a very short period and then stop working again.

also I have some experience repairing phones if it matters.

Any help would be very appreciated.

Thanks in advance

best regards.