diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index d48443181..208cf9b66 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -1430,11 +1430,9 @@ double ModelObject::get_min_z() const
 {
     if (instances.empty())
         return 0.0;
-    else
-    {
+    else {
         double min_z = DBL_MAX;
-        for (size_t i = 0; i < instances.size(); ++i)
-        {
+        for (size_t i = 0; i < instances.size(); ++i) {
             min_z = std::min(min_z, get_instance_min_z(i));
         }
         return min_z;
@@ -1445,15 +1443,14 @@ double ModelObject::get_instance_min_z(size_t instance_idx) const
 {
     double min_z = DBL_MAX;
 
-    ModelInstance* inst = instances[instance_idx];
+    const ModelInstance* inst = instances[instance_idx];
     const Transform3d& mi = inst->get_matrix(true);
 
-    for (const ModelVolume* v : volumes)
-    {
+    for (const ModelVolume* v : volumes) {
         if (!v->is_model_part())
             continue;
 
-        Transform3d mv = mi * v->get_matrix();
+        const Transform3d mv = mi * v->get_matrix();
         const TriangleMesh& hull = v->get_convex_hull();
 		for (const stl_facet &facet : hull.stl.facet_start)
 			for (int i = 0; i < 3; ++ i)
diff --git a/src/slic3r/GUI/3DScene.cpp b/src/slic3r/GUI/3DScene.cpp
index 57ec1e0d9..c64c36ea8 100644
--- a/src/slic3r/GUI/3DScene.cpp
+++ b/src/slic3r/GUI/3DScene.cpp
@@ -524,7 +524,7 @@ bool GLVolume::is_sinking() const
     if (is_modifier)
         return false;
     const BoundingBoxf3& box = transformed_convex_hull_bounding_box();
-    return box.min(2) < 0.0 && box.max(2) >= 0.0;
+    return box.min(2) < -EPSILON && box.max(2) >= -EPSILON;
 }
 
 bool GLVolume::is_below_printbed() const
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 59a4a62a4..1513c5a39 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -3610,18 +3610,30 @@ void GLCanvas3D::do_rotate(const std::string& snapshot_type)
     if (!snapshot_type.empty())
         wxGetApp().plater()->take_snapshot(_(snapshot_type));
 
+#if ENABLE_ALLOW_NEGATIVE_Z
+    // stores current min_z of instances
+    std::map<std::pair<int, int>, double> min_zs;
+    if (!snapshot_type.empty()) {
+        for (int i = 0; i < static_cast<int>(m_model->objects.size()); ++i) {
+            const ModelObject* obj = m_model->objects[i];
+            for (int j = 0; j < static_cast<int>(obj->instances.size()); ++j) {
+                min_zs[{ i, j }] = obj->instance_bounding_box(j).min(2);
+            }
+        }
+    }
+#endif // ENABLE_ALLOW_NEGATIVE_Z
+
     std::set<std::pair<int, int>> done;  // keeps track of modified instances
 
     Selection::EMode selection_mode = m_selection.get_mode();
 
-    for (const GLVolume* v : m_volumes.volumes)
-    {
+    for (const GLVolume* v : m_volumes.volumes) {
         int object_idx = v->object_idx();
         if (object_idx == 1000) { // the wipe tower
             Vec3d offset = v->get_volume_offset();
             post_event(Vec3dEvent(EVT_GLCANVAS_WIPETOWER_ROTATED, Vec3d(offset(0), offset(1), v->get_volume_rotation()(2))));
         }
-        if ((object_idx < 0) || ((int)m_model->objects.size() <= object_idx))
+        if (object_idx < 0 || (int)m_model->objects.size() <= object_idx)
             continue;
 
         int instance_idx = v->instance_idx();
@@ -3631,15 +3643,12 @@ void GLCanvas3D::do_rotate(const std::string& snapshot_type)
 
         // Rotate instances/volumes.
         ModelObject* model_object = m_model->objects[object_idx];
-        if (model_object != nullptr)
-        {
-            if (selection_mode == Selection::Instance)
-            {
+        if (model_object != nullptr) {
+            if (selection_mode == Selection::Instance) {
                 model_object->instances[instance_idx]->set_rotation(v->get_instance_rotation());
                 model_object->instances[instance_idx]->set_offset(v->get_instance_offset());
             }
-            else if (selection_mode == Selection::Volume)
-            {
+            else if (selection_mode == Selection::Volume) {
                 model_object->volumes[volume_idx]->set_rotation(v->get_volume_rotation());
                 model_object->volumes[volume_idx]->set_offset(v->get_volume_offset());
             }
@@ -3648,12 +3657,18 @@ void GLCanvas3D::do_rotate(const std::string& snapshot_type)
     }
 
     // Fixes sinking/flying instances
-    for (const std::pair<int, int>& i : done)
-    {
+    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);
+#if ENABLE_ALLOW_NEGATIVE_Z
+        // leave sinking instances as sinking
+        if (min_zs.empty() || min_zs.find({i.first, i.second})->second >= 0.0) {
+#endif // ENABLE_ALLOW_NEGATIVE_Z
+            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);
+#if ENABLE_ALLOW_NEGATIVE_Z
+        }
+#endif // ENABLE_ALLOW_NEGATIVE_Z
     }
 
     if (!done.empty())