diff --git a/src/kiri/print.js b/src/kiri/print.js
index a10ac733..86056a1a 100644
--- a/src/kiri/print.js
+++ b/src/kiri/print.js
@@ -568,9 +568,6 @@
             if (slice.index < 0) {
                 return false;
             }
-            if (opt.danger) {
-                return retractRequired(p1, p2);
-            }
             let int = false;
             slice.topPolysFlat().forEach(function(poly) {
                 if (!int) poly.forEachSegment(function(s1, s2) {
@@ -579,12 +576,16 @@
                     }
                 });
             });
+            // if intersecting, look for a route around
+            if (int && opt.danger) {
+                return !routeAround(p1, p2);
+            }
             return int;
         }
 
         // returns true if no path around and retract required
         // returns false if routed around or no retract
-        function retractRequired(p1, p2) {
+        function routeAround(p1, p2) {
             const dbug = false;
 
             if (dbug === slice.index) console.log(slice.index, {p1, p2, d: p1.distTo2D(p2)});
@@ -632,6 +633,7 @@
                     return true;
                 }
                 // mark invalid intersect pairs (low or zero dist, etc)
+                // TODO: only if this is the outer pair and there are closer inner pairs
                 if (i1.ip.distTo2D(i2.ip) < retractDist) {
                     if (dbug === slice.index) console.log(slice.index, {int_dist_too_small: i1.ip.distTo2D(i2.ip), retractDist});
                     ints[i] = undefined;
diff --git a/src/kiri/slice.js b/src/kiri/slice.js
index 6419e787..2e2ef02c 100644
--- a/src/kiri/slice.js
+++ b/src/kiri/slice.js
@@ -111,7 +111,7 @@
         if (this.topFlatPolys) {
             return this.topFlatPolys;
         }
-        return this.topFlatPolys = POLY.flatten(this.topPolys()).clone(true);
+        return this.topFlatPolys = POLY.flatten(this.topPolys().clone(true), [], true);
     };
 
     // FDM retract path routing using first shell
@@ -119,7 +119,8 @@
         if (this.topFlatRoutes) {
             return this.topFlatRoutes;
         }
-        return this.topFlatRoutes = POLY.flatten(this.tops.map(top => top.shells[0]).clone(true), [], true);
+        let topShells0 = this.tops.map(top => top.shells[0]).filter(p => p);
+        return this.topFlatRoutes = POLY.flatten(topShells0.clone(true), [], true);
     }
 
     // CAM only
diff --git a/src/mode/fdm/slice.js b/src/mode/fdm/slice.js
index 6eed5231..22b2a426 100644
--- a/src/mode/fdm/slice.js
+++ b/src/mode/fdm/slice.js
@@ -534,7 +534,7 @@
                 .setLayer("gaps", COLOR.gaps)
                 .addPolys(top.gaps, vopt({ offset, height, thin: true }));
 
-            if (isThin && devel) {
+            if (isThin && devel && top.fill_off && top.fill_off.length) {
                 slice.output()
                     .setLayer('fill inset', { face: 0, line: 0xaaaaaa, check: 0xaaaaaa })
                     .addPolys(top.fill_off);