Chan_sip: Register request Retransmission stops after 7 retransmission without any Response

Hello, I am trying to understand why retransmission of REGISTER messages stops after 7 retransmission (before SIP timer expires i.e. 32 sec), it says in the logs that reply received but i can’t see any SIP reply neither in Asterisk logs nor in Wireshark packet capture.
I am getting the following lines in Asterisk logs. (not attaching the whole REGISTER message).
all the Register request mentioned below have the same cSeq.

[Jan 15 12:29:27] DEBUG[3059] chan_sip.c: Reliably Transmitting (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:28] DEBUG[3059] chan_sip.c: SIP timers: Rescheduling retransmission 2 to 1000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:28] VERBOSE[3059] chan_sip.c: Retransmitting #1 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:29] DEBUG[3059] chan_sip.c: ** SIP timers: Rescheduling retransmission 3 to 2000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:29] VERBOSE[3059] chan_sip.c: Retransmitting #2 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:31] DEBUG[3059] chan_sip.c: ** SIP timers: Rescheduling retransmission 4 to 4000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:31] VERBOSE[3059] chan_sip.c: Retransmitting #3 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:35] DEBUG[3059] chan_sip.c: ** SIP timers: Rescheduling retransmission 5 to 4000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:35] VERBOSE[3059] chan_sip.c: Retransmitting #4 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:39] DEBUG[3059] chan_sip.c: ** SIP timers: Rescheduling retransmission 6 to 4000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:39] VERBOSE[3059] chan_sip.c: Retransmitting #5 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:43] DEBUG[3059] chan_sip.c: ** SIP timers: Rescheduling retransmission 7 to 4000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:43] VERBOSE[3059] chan_sip.c: Retransmitting #6 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:47] DEBUG[3059] chan_sip.c: SIP timers: Rescheduling retransmission 8 to 4000 ms (t1 500 ms (Retrans id #804))
[Jan 15 12:29:47] VERBOSE[3059] chan_sip.c: Retransmitting #7 (no NAT) to 10.0.68.2:5060:
REGISTER sip:10.0.68.2 SIP/2.0

[Jan 15 12:29:47] DEBUG[3059] chan_sip.c: SIP TIMER: Cancelling retransmit of packet (reply received) Retransid #804
[Jan 15 12:29:47] DEBUG[3059] chan_sip.c: Stopping retransmission on ‘109eb56401a1e2237bc76d077b8227ed@172.17.251.9’ of Request 2198: Match Found
[Jan 15 12:29:47] DEBUG[3059] chan_sip.c: OBPROXY: Not applying OBproxy to this call