I have strange issue where some shared lines will start showing there is an active call on them (icon next to line number on phone, or red light on 7914 sidecar). The lines that have this problem are in a pickup group also.
The phone is able to place/receive calls fine, so this appears to be a display/cosmetic issue at this time.
The only thing I have found to clear this so far, for awhile, is to teboot the router.
It is a 2811 with 12.4(4)XC2 IOS
load 7910 P00403020214
load 7935 P00503010100
load 7960-7940 P00307020200
load 7914 S00104000100
load ATA ATA030100SCCP040211A.zup
load 7905 CP7905010200SCCP031023A.sbin
load 7902 CP7902010200SCCP031023A.sbin
load 7920 cmterm_7920.3.3-01-07.bin
load 7912 CP7912060000SCCP050124A.sbin
Sample DN config of one of the lines.
ephone-dn 64 dual-line
label DF 6235
call-forward busy 8000
call-forward noan 8000 timeout 20
I have also tried to reset the phone, remove the pickup group and add it back, etc and only a router reboot appears to clear this for awhile.