Changing this to an Enhancement request.

Ah. I see. Turba only stores a single phone number in each phone 
number field that you configure. I.e., you can only have one "Home" 
phone number or one "Office" phone number.  Older ActiveSync clients 
only allowed this too, but it looks like this is changing. If you want 
to support this with you'd have to implement multi-phone number field 
support in Turba.

I use the Active Sync (Exchange) protocol.
The client applications is the default "Kontakte" (Contacts) at 
Android 8 (CAT S41).
The simplest steps to reproduce are the following.
1. Create a contact with a name and 2 different private phone numbers 
at the phone
2. Sync the contact to the horde server
3. Open the contact via horde webinterface
=> There are 2 entrys for a private phone number, but only one number 
is filled in.

Just verified that adding a new "Home" phone number to an existing 
contact that does not have a Home phone number (while other contacts 
in the address book do) works fine. Similarly using "Mobile" and 
"Office" also work.

Marking as not reproducible until steps to reproduce are provided.

With what protocol are you synchronizing your devices? What client 
application is being used? Are you adding an additional phone number 
to the contact? What do you mean by "assign a category"?  Please 
provide a step-by-step way to reproduce.

I'm synchronizing my horde server (calendar and contacts) with 3 equal 
Android phones (CAT S41). When I add a telephone number to an already 
existing contact and use a category which I already used in this 
contact for another phone number (like privat), then the new number 
will not be synced to the other phones.