I took my phone to a local repair shop today, and they told me it is not a problem with the cable - we see the same problem when using their cable.
The guy in the repair shop thinks the battery is broken. As I got the phone in February, this is early, but he said this can happen. It might (my own thought) be some connector soldering etc. but I’m now filing a warranty claim to Fairphone customer support.
In the end, my talks with Fairphone Support ended in me sending the phone to them for assessment.
I expect to get a repaired phone back, or a replacement. I actually had the opportunity to swap batteries with a colleague, and it didn’t work - so it’s the internal wiring, not the battery.
I might as well wrap up this thread by saying that my phone finally came back from warranty repair and is now charging!
I haven’t as such put in a SIM card yet, because I’ve got used to using my Fairphone2 with Bluetooth earbuds instead of the broken microphone. I expect to flash it and install /e/ to get a more free software-oriented version.
I had the same problem: very slowly charging, no data transfer. My fairphone 3 is one year old. I first tried the solutions to clean the usb-port, to try another cable, to connect to a PC instead of socket. No result.
The very nice supporter of fairphone offered to repair it without costs within the warranty, but this would have lasted two weeks inclusive shipping time. Too long .
As the data transfer did not work it was clear for me that it was not the battery but the bottom module.
I bought a bottom module over amazon from i-sell everything went fine and easy at cost of 28,83 EUR. Original part!
I learned from the video how to change the bottom module - very easy.
And everything works again as it should do. Great relief!!
It is good to have a phone that can be repaired easily!!
BUT:
Problems with a central module of a fairphone only after one year of use: not very satisfiying!
No refund of my costs by fairphone, although I dif the rapiring work by myself: Not very satisfying.
@anon9989719’s proposal is the only way in which I see perhaps still happening what you want.
Fairphone (or their repair center for that matter) need to check out the module for themselves to be able to acknowledge a warranty case, i.e. making sure there’s no water damage or physical destruction involved or anything else excluded from the warranty.
Else they would basically hand out free modules for every possible user fault, which is not how it’s supposed to work. The world isn’t populated by only nice/ honest/ reasonable people, even if they have a Fairphone, and Fairphone don’t run a charity, so sensible processes need to be in place .
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