Can't open an afp networkshare (but other machines can)

[Morris]

I've spent the last few months (on and off) trying to get an afp networkshare to work using netatalk on OpenWrt. It takes a bit of work and it's easy to make mistakes so, when I couldn't connect to one of the shares from my MBP, I initially assumed that I made a configuration error. I created two shares that are essentially identical (except that one is for Time Machine and uses different user credentials) and the second share is fine. Strangely enough on my girlfriend's MBP both shares work fine.

Let's call my machine MBP-A and my girlfriend's machine MBP-B, both are running High Sierra. Let's call the share that's not working "TimeMachine" and the working second share "Data".

• MBP-A can't connect to TimeMachine using Cmd-K in the Finder "The share does not exist on the server. Please check the share name, and then try again."
• MBP-A connects to "Data" just fine. I get a prompt for username and password, I enter them and the machine connects.
• MBP-B can connect to both shares just fine. I get a prompt for username and password, I enter them and the machine connects. I have also been able to point Time Machine to the "Time Machine" share and that is running a backup as we speak.
• When I try to mount the problematic share in Terminal

  sudo mount -t afp afp://user:password@192.168.1.1/TimeMachine /Volumes/TimeMachine

  it does mount it to a newly created local dir called /Volumes/TimeMachine. I can see the available space in /Volumes/TimeMachine in the Finder and can see that space decrease because the other machine is making a backup to it as we speak. If I want to enter the folder from the Finder, however, I get "The folder “TimeMachine” can’t be opened because you don’t have permission to see its contents."

This leads me to believe that it's not a configuration problem on the server side as it works fine on the other machine but that it's a local problem on my machine. I thought it might have cached the wrong credentials but they are not in the keychain and the problem persists after a reboot.

Any ideas?