In the old network cutover, it may be related to the old cisco equipment reserve, in the old IOS, it may not support the BFD, please do use the SLA link detection, configuration is as follows:
ip sla 1
icmp-echo 10.185.252.41 source-interface FastEthernet0/1
timeout 6000
frequency 10
ip sla schedule 1 life forever start-time now
track 1 ip sla 1 reachability
ip route 0.0.0.0 0.0.0.0 172.16.5.1 track 1 // note, track id and the id must be consistent sla