diff --git a/src/libslic3r/Brim.cpp b/src/libslic3r/Brim.cpp
index a13d578a3..8f31b0695 100644
--- a/src/libslic3r/Brim.cpp
+++ b/src/libslic3r/Brim.cpp
@@ -114,6 +114,7 @@ static ConstPrintObjectPtrs get_top_level_objects_with_brim(const Print &print,
     clipper.AddPaths(islands_clip, ClipperLib_Z::ptSubject, true);
     // Execute union operation to construct polytree
     ClipperLib_Z::PolyTree islands_polytree;
+    //FIXME likely pftNonZero or ptfPositive would be better. Why are we using ptfEvenOdd for Unions?
     clipper.Execute(ClipperLib_Z::ctUnion, islands_polytree, ClipperLib_Z::pftEvenOdd, ClipperLib_Z::pftEvenOdd);
 
     std::unordered_set<size_t> processed_objects_idx;
@@ -486,7 +487,7 @@ ExtrusionEntityCollection make_brim(const Print &print, PrintTryCancel try_cance
 		    clipper.AddPaths(input_subject, ClipperLib_Z::ptSubject, true);
 		    clipper.AddPaths(input_clip,    ClipperLib_Z::ptClip,    true);
 		    // perform operation
-		    clipper.Execute(ClipperLib_Z::ctDifference, trimming, ClipperLib_Z::pftEvenOdd, ClipperLib_Z::pftEvenOdd);
+		    clipper.Execute(ClipperLib_Z::ctDifference, trimming, ClipperLib_Z::pftNonZero, ClipperLib_Z::pftNonZero);
 		}
 
 		// Second, trim the extrusion loops with the trimming regions.
@@ -515,7 +516,7 @@ ExtrusionEntityCollection make_brim(const Print &print, PrintTryCancel try_cance
 			clipper.AddPaths(trimming,   ClipperLib_Z::ptClip,    true);
 			// perform operation
 			ClipperLib_Z::PolyTree loops_trimmed_tree;
-			clipper.Execute(ClipperLib_Z::ctDifference, loops_trimmed_tree, ClipperLib_Z::pftEvenOdd, ClipperLib_Z::pftEvenOdd);
+			clipper.Execute(ClipperLib_Z::ctDifference, loops_trimmed_tree, ClipperLib_Z::pftNonZero, ClipperLib_Z::pftNonZero);
 			ClipperLib_Z::PolyTreeToPaths(loops_trimmed_tree, loops_trimmed);
 		}
 
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 2e3de778e..232e724e7 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -3970,10 +3970,16 @@ std::string validate(const FullPrintConfig &cfg)
         if (em <= 0)
             return "Invalid value for --extrusion-multiplier";
 
+    // The following test was commented out after 482841b, see also https://github.com/prusa3d/PrusaSlicer/pull/6743.
+    // The backend should now handle this case correctly. I.e., zero default_acceleration behaves as if all others
+    // were zero too. This is now consistent with what the UI said would happen.
+    // The UI already grays the fields out, there is no more reason to reject it here. This function validates the
+    // config before exporting, leaving this check in would mean that config would be rejected before export
+    // (although both the UI and the backend handle it).
     // --default-acceleration
-    if ((cfg.perimeter_acceleration != 0. || cfg.infill_acceleration != 0. || cfg.bridge_acceleration != 0. || cfg.first_layer_acceleration != 0.) &&
-        cfg.default_acceleration == 0.)
-        return "Invalid zero value for --default-acceleration when using other acceleration settings";
+    //if ((cfg.perimeter_acceleration != 0. || cfg.infill_acceleration != 0. || cfg.bridge_acceleration != 0. || cfg.first_layer_acceleration != 0.) &&
+    //    cfg.default_acceleration == 0.)
+    //    return "Invalid zero value for --default-acceleration when using other acceleration settings";
 
     // --spiral-vase
     if (cfg.spiral_vase) {
diff --git a/src/libslic3r/SLA/ConcaveHull.cpp b/src/libslic3r/SLA/ConcaveHull.cpp
index cfce36d16..08a2ff676 100644
--- a/src/libslic3r/SLA/ConcaveHull.cpp
+++ b/src/libslic3r/SLA/ConcaveHull.cpp
@@ -133,7 +133,8 @@ ExPolygons offset_waffle_style_ex(const ConcaveHull &hull, coord_t delta)
 
 Polygons offset_waffle_style(const ConcaveHull &hull, coord_t delta)
 {
-    Polygons res = closing(hull.polygons(), 2 * delta, delta, ClipperLib::jtRound);
+    auto arc_tolerance = scaled<double>(0.01);
+    Polygons res = closing(hull.polygons(), 2 * delta, delta, ClipperLib::jtRound, arc_tolerance);
 
     auto it = std::remove_if(res.begin(), res.end(), [](Polygon &p) { return p.is_clockwise(); });
     res.erase(it, res.end());