I have had the same issue on 2 new FreePBX installs with Commercial Endpoint Manager installed.
Phones provision happily EXCEPT the BLF side of things.
I create BLFs to monitor extensions and do call parking and set all to account 1
What happens though is the account numbers on the phone handset increment.
On DSS key page of yealink, Line one get account N/A, Line 2 gets account 1, Line 3 get account 3 and so on.
Anyone else come across this?
Both are new installs of FreePBX within the last month.
Using latest firmware on phones provided by EPM and latest distro.
All system and module updates are done.