Next hop changing from global IPv6 address to IPv4-mapped IPv6 address (spontaneously?)

[jcaamano]

On a BGP session over IPv6, the next hop announced to peer changes from the global IPv6 address used to establish the session changed to IPv4-mapped IPv6 address. The change is apparently spontaneous, no meaningful activity is observed in system/frr logs that clues me in on why this happens. I am rather inexperienced with FRR so I will need a bit of guidance in terms of what useful information I can provide.

This is the neighbor information towards the peer

BGP neighbor is fd2e:6f44:5dd8:c956::1, remote AS 64512, local AS 64512, internal link
  Local Role: undefined
  Remote Role: undefined
Hostname: openshift-qe-026.lab.eng.rdu2.redhat.com
  BGP version 4, remote router ID 192.168.222.1, local router ID 192.168.111.23
  BGP state = Established, up for 03:23:48
  Last read 00:00:48, Last write 00:00:48
  Hold time is 180 seconds, keepalive interval is 60 seconds
  Configured hold time is 180 seconds, keepalive interval is 60 seconds
  Configured conditional advertisements interval is 60 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    Extended Message: advertised and received
    AddPath:
      IPv6 Unicast: RX advertised and received
    Long-lived Graceful Restart: advertised and received
      Address families by peer:
    Route refresh: advertised and received(new)
    Enhanced Route Refresh: advertised and received
    Address Family IPv6 Unicast: advertised and received
    Hostname Capability: advertised (name: worker-0.offload.openshift-qe.sdn.com,domain name: n/a) received (name: openshift-qe-026.lab.eng.rdu2.redhat.com,domain name: n/a)
    Graceful Restart Capability: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv6 Unicast
    End-of-RIB received: IPv6 Unicast
    Local GR Mode: Helper*

    Remote GR Mode: Helper

    R bit: True
    N bit: True
    Timers:
      Configured Restart Time(sec): 120
      Received Restart Time(sec): 120
    IPv6 Unicast:
      F bit: False
      End-of-RIB sent: Yes
      End-of-RIB sent after update: No
      End-of-RIB received: Yes
      Timers:
        Configured Stale Path Time(sec): 360
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  1          1
    Notifications:          0          0
    Updates:                4         12
    Keepalives:           204        204
    Route Refresh:          1          2
    Capability:             0          0
    Total:                210        219
  Minimum time between advertisement runs is 0 seconds

 For address family: IPv6 Unicast
  Update group 4, subgroup 4
  Packet Queue length 0
  Community attribute sent to this neighbor(all)
  Inbound path policy configured
  Outbound path policy configured
  Route map for incoming advertisements is *fd2e:6f44:5dd8:c956::1-in
  Route map for outgoing advertisements is *fd2e:6f44:5dd8:c956::1-out
  8 accepted prefixes

  Connections established 1; dropped 0
  Last reset 03:23:52,  Waiting for peer OPEN
  Internal BGP neighbor may be up to 255 hops away.
Local host: fd2e:6f44:5dd8:c956::17, Local port: 40388
Foreign host: fd2e:6f44:5dd8:c956::1, Foreign port: 179
Nexthop: 192.168.111.23
Nexthop global: ::ffff:c0a8:6f17
Nexthop local: ::
BGP connection: non shared network
BGP Connect Retry Timer in Seconds: 120
Estimated round trip time: 0 ms
Read thread: on  Write thread: on  FD used: 24

That started out being

Nexthop global: fd2e:6f44:5dd8:c956::17

I don't know how to track why and when it changed to

Nexthop global: ::ffff:c0a8:6f17

FRR version: 9.1.2

Any help appreciated. Thanks!