Win10 Sync center, offline files and VPN

In short : Why, when I activate the offline files save for a given subdirectory located in a network directory accessible over VPN, it is not possible anymore to access the rest of the main network directory over VPN?

In more details :

1. I start my VPN and gain access to all my office network and one of its drive is mapped X:/.
2. I activate the offline files save for a specific subfolder, such as 'X:/Sub1/' using the Windows Sync center
3. I end my VPN connection and i do not have access to the network drives anymore, only the X:/Sub1/ is still accessible, which is expected and normal.
4. I re-start my VPN and normally, i would instantly regain access to all the network drives, but it does not anymore. All the other network drives, including all other X:/ subfolders are greyed out and not accessible, except the one offline saved.

My only option is thus to de-activate Offline files saving in order to find back the initial and functionnal behavior of my VPN and network access.

It's like it is impossible to combine both features, which seems to defeat the purpose?

Anyone knows a thing about this?
I'm actually looking to save some of our office network subfolders on my local machine so my software would work faster with the project files saved on the network (and not having to copy and move them every time). I'm not looking to work fully offline. I think 3rd party apps does these kinds of 2-way syncs, but i thought this built-in Microsoft Sync thing would do the trick.

(PS, i'm not the network manager, but i Know we are using a Windows Server 2012)

Thanks,

(I've found this post which seems to answer my question... is it always realted to the VPN?)