diff --git a/src/libslic3r/PrintApply.cpp b/src/libslic3r/PrintApply.cpp
index 49909ec270..e4f421414a 100644
--- a/src/libslic3r/PrintApply.cpp
+++ b/src/libslic3r/PrintApply.cpp
@@ -1205,6 +1205,13 @@ Print::ApplyStatus Print::apply(const Model &model, DynamicPrintConfig new_full_
     DynamicPrintConfig   filament_overrides;
     //BBS: add plate index
     t_config_option_keys print_diff       = print_config_diffs(m_config, new_full_config, filament_overrides, this->m_plate_index, filament_maps);
+    // Orca: filament_map_2 is engine-derived state, never a user input: the rebuild below
+    // recomputes it from filament_map/filament_volume_map/the variant slots on every apply
+    // (all of which are diffed and invalidation-listed on their own), and the grouping
+    // write-back overwrites it during process(). The incoming full config only ever carries
+    // the ConfigDef default, so diffing it would invalidate every print step on each apply
+    // for any multi-extruder printer and permanently invalidate fresh slice results.
+    print_diff.erase(std::remove(print_diff.begin(), print_diff.end(), "filament_map_2"), print_diff.end());
     t_config_option_keys full_config_diff = full_print_config_diffs(m_full_print_config, new_full_config, this->m_plate_index);
     // Collect changes to object and region configs.
     t_config_option_keys object_diff      = m_default_object_config.diff(new_full_config);
diff --git a/tests/libslic3r/test_toolordering_nozzle_group.cpp b/tests/libslic3r/test_toolordering_nozzle_group.cpp
index fbc05d811f..dcc2ae9521 100644
--- a/tests/libslic3r/test_toolordering_nozzle_group.cpp
+++ b/tests/libslic3r/test_toolordering_nozzle_group.cpp
@@ -460,3 +460,39 @@ TEST_CASE("Print config-index resolvers pick per-filament Hybrid slots", "[Print
         REQUIRE(print.get_nozzle_config_index(2, 0) == 1); // extruder slot, not the High Flow slot
     }
 }
+
+TEST_CASE("Re-applying an unchanged config after slicing keeps the result valid", "[Print][H2C]")
+{
+    // apply() rebuilds m_config.filament_map_2 to the real per-filament slot map, while the
+    // incoming full config only ever carries the ConfigDef default for it. The engine-derived
+    // key must therefore be kept out of the apply diff: the GUI re-applies right after slicing
+    // completes, and a phantom filament_map_2 diff would invalidate every freshly sliced result
+    // on any multi-extruder printer.
+    DynamicPrintConfig config = DynamicPrintConfig::full_print_config();
+    config.option<ConfigOptionFloats>("nozzle_diameter", true)->values = {0.4, 0.4};
+    config.option<ConfigOptionStrings>("extruder_nozzle_stats", true)->values = {"Standard#1", "Standard#1|High Flow#2"};
+    config.option<ConfigOptionEnumsGeneric>("extruder_type", true)->values = {etDirectDrive, etDirectDrive};
+    config.option<ConfigOptionEnumsGeneric>("nozzle_volume_type", true)->values = {nvtStandard, nvtHybrid};
+    config.option<ConfigOptionStrings>("extruder_variant_list", true)->values = {"Direct Drive Standard,Direct Drive High Flow",
+                                                                                 "Direct Drive Standard,Direct Drive High Flow"};
+    config.option<ConfigOptionInts>("print_extruder_id", true)->values = {1, 1, 2, 2};
+    config.option<ConfigOptionStrings>("print_extruder_variant", true)->values = {"Direct Drive Standard", "Direct Drive High Flow",
+                                                                                  "Direct Drive Standard", "Direct Drive High Flow"};
+    config.option<ConfigOptionFloats>("filament_diameter", true)->values = {1.75, 1.75, 1.75};
+    config.option<ConfigOptionStrings>("filament_colour", true)->values = {"#FF0000", "#00FF00", "#0000FF"};
+    config.option<ConfigOptionInts>("filament_map", true)->values = {1, 2, 2};
+    config.option<ConfigOptionInts>("filament_volume_map", true)->values = {(int) nvtStandard, (int) nvtStandard, (int) nvtHighFlow};
+
+    Model model;
+    ModelObject *object = model.add_object("cube", "", make_cube(20, 20, 20));
+    object->add_instance()->set_offset(Vec3d(100., 100., 0.));
+
+    Print print;
+    print.apply(model, config);
+    print.process();
+    REQUIRE(print.is_step_done(psSlicingFinished));
+
+    auto status = print.apply(model, config);
+    REQUIRE(status != PrintBase::APPLY_STATUS_INVALIDATED);
+    REQUIRE(print.is_step_done(psSlicingFinished));
+}