diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 208516536..f0a29faa4 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1080,8 +1080,10 @@ GLCanvas3D::Selection::VolumeCache::TransformCache::TransformCache()
     : position(Vec3d::Zero())
     , rotation(Vec3d::Zero())
     , scaling_factor(Vec3d::Ones())
+    , mirror(Vec3d::Ones())
     , rotation_matrix(Transform3d::Identity())
     , scale_matrix(Transform3d::Identity())
+    , mirror_matrix(Transform3d::Identity())
 {
 }
 
@@ -1089,9 +1091,11 @@ GLCanvas3D::Selection::VolumeCache::TransformCache::TransformCache(const Geometr
     : position(transform.get_offset())
     , rotation(transform.get_rotation())
     , scaling_factor(transform.get_scaling_factor())
+    , mirror(transform.get_mirror())
 {
     rotation_matrix = Geometry::assemble_transform(Vec3d::Zero(), rotation);
     scale_matrix = Geometry::assemble_transform(Vec3d::Zero(), Vec3d::Zero(), scaling_factor);
+    mirror_matrix = Geometry::assemble_transform(Vec3d::Zero(), Vec3d::Zero(), Vec3d::Ones(), mirror);
 }
 
 GLCanvas3D::Selection::VolumeCache::VolumeCache(const Geometry::Transformation& volume_transform, const Geometry::Transformation& instance_transform)
@@ -1481,7 +1485,7 @@ void GLCanvas3D::Selection::translate(const Vec3d& displacement)
 #if ENABLE_MODELVOLUME_TRANSFORM
     if ((m_mode == Volume) || (*m_volumes)[i]->is_wipe_tower)
     {
-        Vec3d local_displacement = (m_cache.volumes_data[i].get_instance_rotation_matrix() * m_cache.volumes_data[i].get_instance_scale_matrix()).inverse() * displacement;
+        Vec3d local_displacement = (m_cache.volumes_data[i].get_instance_rotation_matrix() * m_cache.volumes_data[i].get_instance_scale_matrix() * m_cache.volumes_data[i].get_instance_mirror_matrix()).inverse() * displacement;
         (*m_volumes)[i]->set_volume_offset(m_cache.volumes_data[i].get_volume_position() + local_displacement);
     }
     else if (m_mode == Instance)
@@ -5338,6 +5342,15 @@ void GLCanvas3D::do_mirror()
         }
     }
 
+    // Fixes sinking/flying instances
+    for (const std::pair<int, int>& i : done)
+    {
+        ModelObject* m = m_model->objects[i.first];
+        Vec3d shift(0.0, 0.0, -m->get_instance_min_z(i.second));
+        m_selection.translate(i.first, i.second, shift);
+        m->translate_instance(i.second, shift);
+    }
+
     post_event(SimpleEvent(EVT_GLCANVAS_SCHEDULE_BACKGROUND_PROCESS));
 }
 
diff --git a/src/slic3r/GUI/GLCanvas3D.hpp b/src/slic3r/GUI/GLCanvas3D.hpp
index d43fff271..44b5468a5 100644
--- a/src/slic3r/GUI/GLCanvas3D.hpp
+++ b/src/slic3r/GUI/GLCanvas3D.hpp
@@ -398,8 +398,10 @@ public:
                 Vec3d position;
                 Vec3d rotation;
                 Vec3d scaling_factor;
+                Vec3d mirror;
                 Transform3d rotation_matrix;
                 Transform3d scale_matrix;
+                Transform3d mirror_matrix;
 
                 TransformCache();
                 explicit TransformCache(const Geometry::Transformation& transform);
@@ -428,14 +430,18 @@ public:
             const Vec3d& get_volume_position() const { return m_volume.position; }
             const Vec3d& get_volume_rotation() const { return m_volume.rotation; }
             const Vec3d& get_volume_scaling_factor() const { return m_volume.scaling_factor; }
+            const Vec3d& get_volume_mirror() const { return m_volume.mirror; }
             const Transform3d& get_volume_rotation_matrix() const { return m_volume.rotation_matrix; }
             const Transform3d& get_volume_scale_matrix() const { return m_volume.scale_matrix; }
+            const Transform3d& get_volume_mirror_matrix() const { return m_volume.mirror_matrix; }
 
             const Vec3d& get_instance_position() const { return m_instance.position; }
             const Vec3d& get_instance_rotation() const { return m_instance.rotation; }
             const Vec3d& get_instance_scaling_factor() const { return m_instance.scaling_factor; }
+            const Vec3d& get_instance_mirror() const { return m_instance.mirror; }
             const Transform3d& get_instance_rotation_matrix() const { return m_instance.rotation_matrix; }
             const Transform3d& get_instance_scale_matrix() const { return m_instance.scale_matrix; }
+            const Transform3d& get_instance_mirror_matrix() const { return m_instance.mirror_matrix; }
 #else
             const Vec3d& get_position() const { return m_position; }
             const Vec3d& get_rotation() const { return m_rotation; }