diff --git a/plugins/channel-safely/channel-groups.cpp b/plugins/channel-safely/channel-groups.cpp
index 52f7e6c40..8f7f4b117 100644
--- a/plugins/channel-safely/channel-groups.cpp
+++ b/plugins/channel-safely/channel-groups.cpp
@@ -119,7 +119,13 @@ void ChannelGroups::scan_one(const df::coord &map_pos) {
 }
 
 // builds groupings of adjacent channel designations
-void ChannelGroups::scan() {
+void ChannelGroups::scan(bool full_scan) {
+    static std::default_random_engine RNG(0);
+    static std::bernoulli_distribution sometimes_scanFULLY(0.15);
+    if (!full_scan) {
+        full_scan = sometimes_scanFULLY(RNG);
+    }
+
     // save current jobs, then clear and load the current jobs
     std::set<df::coord> last_jobs;
     for (auto &pos : jobs) {
@@ -138,9 +144,6 @@ void ChannelGroups::scan() {
         remove(pos);
     }
 
-    static std::default_random_engine RNG(0);
-    static std::bernoulli_distribution optimizing(0.75); // fixing OpenSpace as designated
-
     DEBUG(groups).print("  scan()\n");
     // foreach block
     for (int32_t z = mapz - 1; z >= 0; --z) {
@@ -149,7 +152,7 @@ void ChannelGroups::scan() {
                 // the block
                 if (df::map_block* block = Maps::getBlock(bx, by, z)) {
                     // skip this block?
-                    if (!block->flags.bits.designated && !group_blocks.count(block) && optimizing(RNG)) {
+                    if (!full_scan && !block->flags.bits.designated) {
                         continue;
                     }
                     // foreach tile
@@ -165,7 +168,7 @@ void ChannelGroups::scan() {
                                     jobs.erase(map_pos);
                                 }
                                 block->designation[lx][ly].bits.dig = df::tile_dig_designation::No;
-                            } else if (is_dig_designation(block->designation[lx][ly])) {
+                            } else if (is_dig_designation(block->designation[lx][ly]) || block->occupancy[lx][ly].bits.dig_marked) {
                                 for (df::block_square_event* event: block->block_events) {
                                     if (auto evT = virtual_cast<df::block_square_event_designation_priorityst>(event)) {
                                         // we want to let the user keep some designations free of being managed
diff --git a/plugins/channel-safely/channel-safely-plugin.cpp b/plugins/channel-safely/channel-safely-plugin.cpp
index d291c0efc..8af90c335 100644
--- a/plugins/channel-safely/channel-safely-plugin.cpp
+++ b/plugins/channel-safely/channel-safely-plugin.cpp
@@ -1,7 +1,7 @@
 /* Prevent channeling down into known open space.
 Author:  Josh Cooper
 Created: Aug. 4 2020
-Updated: Nov. 6 2022
+Updated: Nov. 28 2022
 
  Enable plugin:
  -> build groups
@@ -225,10 +225,10 @@ namespace CSP {
         active_workers.clear();
     }
 
-    void UnpauseEvent(){
+    void UnpauseEvent(bool full_scan = false){
         CoreSuspender suspend; // we need exclusive access to df memory and this call stack doesn't already have a lock
         INFO(monitor).print("UnpauseEvent()\n");
-        ChannelManager::Get().build_groups();
+        ChannelManager::Get().build_groups(full_scan);
         ChannelManager::Get().manage_groups();
         ChannelManager::Get().debug();
         INFO(monitor).print("UnpauseEvent() exits\n");
@@ -566,9 +566,12 @@ DFhackCExport command_result plugin_onstatechange(color_ostream &out, state_chan
             }
             break;
         case SC_MAP_LOADED:
+        case SC_WORLD_LOADED:
             // cache the map size
             Maps::getSize(mapx, mapy, mapz);
-        case SC_WORLD_LOADED:
+            CSP::ClearData();
+            ChannelManager::Get().build_groups(true);
+            break;
         case SC_WORLD_UNLOADED:
         case SC_MAP_UNLOADED:
             CSP::ClearData();
@@ -587,11 +590,11 @@ DFhackCExport command_result plugin_onupdate(color_ostream &out, state_change_ev
 command_result channel_safely(color_ostream &out, std::vector<std::string> &parameters) {
     if (!parameters.empty()) {
         if (parameters[0] == "runonce") {
-            CSP::UnpauseEvent();
+            CSP::UnpauseEvent(true);
             return DFHack::CR_OK;
         } else if (parameters[0] == "rebuild") {
             ChannelManager::Get().destroy_groups();
-            ChannelManager::Get().build_groups();
+            ChannelManager::Get().build_groups(true);
         }
         if (parameters.size() >= 2 && parameters.size() <= 3) {
             bool state = false;
diff --git a/plugins/channel-safely/include/channel-groups.h b/plugins/channel-safely/include/channel-groups.h
index 7547e2564..8e3224c98 100644
--- a/plugins/channel-safely/include/channel-groups.h
+++ b/plugins/channel-safely/include/channel-groups.h
@@ -39,7 +39,7 @@ protected:
 public:
     explicit ChannelGroups(ChannelJobs &jobs) : jobs(jobs) { groups.reserve(200); }
     void scan_one(const df::coord &map_pos);
-    void scan();
+    void scan(bool full_scan = false);
     void clear();
     void remove(const df::coord &map_pos);
     Groups::const_iterator find(const df::coord &map_pos) const;
diff --git a/plugins/channel-safely/include/channel-manager.h b/plugins/channel-safely/include/channel-manager.h
index 0cd3abfac..323ce8468 100644
--- a/plugins/channel-safely/include/channel-manager.h
+++ b/plugins/channel-safely/include/channel-manager.h
@@ -23,7 +23,7 @@ public:
         return instance;
     }
 
-    void build_groups() { groups.scan(); debug(); }
+    void build_groups(bool full_scan = false) { groups.scan(full_scan); debug(); }
     void destroy_groups() { groups.clear(); debug(); }
     void manage_groups();
     void manage_group(const df::coord &map_pos, bool set_marker_mode = false, bool marker_mode = false);