fix: lagging code

base_layer/core/src/base_node/state_machine_service/states/listening.rs

@@ -380,19 +380,24 @@ fn determine_sync_mode(
         }
 
         // This is to test the block propagation by delaying lagging.
-        if local_tip_height.saturating_add(blocks_behind_before_considered_lagging) > network_tip_height {
-            info!(
+        // If the config is 0, ignore this set.
+        if blocks_behind_before_considered_lagging > 0 {
+            // Otherwise, only wait when the tip is above us, otherwise
+            // chains with a lower height will never be reorged to.
+            if network_tip_height > local_tip_height && local_tip_height.saturating_add(blocks_behind_before_considered_lagging) > network_tip_height {
+                info!(
                 target: LOG_TARGET,
                 "While we are behind, we are still within {} blocks of them, so we are staying as listening and \
                  waiting for the propagated blocks",
                 blocks_behind_before_considered_lagging
             );
-            return SyncStatus::BehindButNotYetLagging {
-                local: local.clone(),
-                network: network.claimed_chain_metadata().clone(),
-                sync_peers: vec![network.clone().into()],
+                return SyncStatus::BehindButNotYetLagging {
+                    local: local.clone(),
+                    network: network.claimed_chain_metadata().clone(),
+                    sync_peers: vec![network.clone().into()],
+                };
             };
-        };
+        }
 
         debug!(
             target: LOG_TARGET,