What phones do you have and what firmware are they on.
If the BLF’s are getting stuck after an asterisk restart then it might be related to my issue.
Yealinks V82+ are following an RFC standard strictly and if you restart asterisk it causes BLF’s to be stuck: https://community.freepbx.org/t/blfs-not-working-right-with-yealink-83-0-x-firmware-response-from-yealink/52012
There is an asterisk bug ticket here if it is your issue, vote for it if it is: https://issues.asterisk.org/jira/browse/ASTERISK-27759