This counts LTRs arriving at this device that do not correlate to any linktrace session this device remembers initiating, analogous to the unexpected-LBR counter but for path-trace responses instead of loopback responses. This can happen when a linktrace's transaction ID has already timed out locally but a slow hop's reply is still working its way back, or, less commonly, when a stale reply from a much earlier session finally arrives. Because linktrace across many hops naturally has more variable round-trip time than a simple loopback, this counter is somewhat more likely to tick up on long, high-hop-count traces than on short local ones.