Did you write the link records in the ApplianceLinc for buttons 3 & 4? The Set button process took care of that for buttons 1 & 2. The ApplianceLinc link records for buttons 3 & 4 have to be done manually, just as you did in the EZX10RF for buttons 3 & 4. Also the X10 Code records in the EZX10RF have to be established for X10 buttons 3 & 4 with Group numbers that match those in the link records for those buttons. The Set button process did this for buttons 1 & 2.
The display of link records by the SHN Utility is sending commands to the PLM part of the EZX10RF. That would suggest a PLM hang problem but that is not absolute.
I think the hang up is an issue with the device, either the EZX10RF firmware or the internal PLM firmware. The problem with buttons 3 & 4 are a definition problem. Either missing link records in the ApplianceLinc or incorrect or missing X10 Code records in the EZX10RF.
The request for a device update can be ordered online through Products | Services. The fourth option in the list of Services.