Don't raise MMU error screen until retry is done

Change in memory:
Flash: +8 bytes
SRAM: 0 bytes

Firmware/mmu2.cpp

@@ -221,15 +221,20 @@ void MMU2::mmu_loop() {
         return;
     avoidRecursion = true;
 
-    logicStepLastStatus = LogicStep(); // it looks like the mmu_loop doesn't need to be a blocking call
+    mmu_loop_inner(true);
+
+    avoidRecursion = false;
+}
+
+void __attribute__((noinline)) MMU2::mmu_loop_inner(bool reportErrors)
+{
+    logicStepLastStatus = LogicStep(reportErrors); // it looks like the mmu_loop doesn't need to be a blocking call
 
     if (is_mmu_error_monitor_active){
         // Call this every iteration to keep the knob rotation responsive
         // This includes when mmu_loop is called within manage_response
         ReportErrorHook((uint16_t)lastErrorCode);
     }
-
-    avoidRecursion = false;
 }
 
 void MMU2::CheckFINDARunout()
@@ -630,9 +635,10 @@ void MMU2::ResumeHotendTemp() {
         lcd_display_message_fullscreen_P(_i("MMU Retry: Restoring temperature...")); ////MSG_MMU_RESTORE_TEMP c=20 r=4
         //@todo better report the event and let the GUI do its work somewhere else
         ReportErrorHookSensorLineRender();
-        waitForHotendTargetTemp(1000, []{
-            ReportErrorHookDynamicRender();
+        waitForHotendTargetTemp(100, []{
             manage_inactivity(true);
+            mmu2.mmu_loop_inner(false);
+            ReportErrorHookDynamicRender();
         });
         lcd_update_enable(true); // temporary hack to stop this locking the printer...
         LogEchoEvent_P(PSTR("Hotend temperature reached"));
@@ -762,7 +768,7 @@ void MMU2::manage_response(const bool move_axes, const bool turn_off_nozzle) {
     }
 }
 
-StepStatus MMU2::LogicStep() {
+StepStatus MMU2::LogicStep(bool reportErrors) {
     CheckUserInput(); // Process any buttons before proceeding with another MMU Query
     StepStatus ss = logic.Step();
     switch (ss) {
@@ -773,30 +779,36 @@ StepStatus MMU2::LogicStep() {
     case Processing:
         OnMMUProgressMsg(logic.Progress());
         break;
-    case CommandError:
-        ReportError(logic.Error(), ErrorSourceMMU);
-        break;
-    case CommunicationTimeout:
-        state = xState::Connecting;
-        ReportError(ErrorCode::MMU_NOT_RESPONDING, ErrorSourcePrinter);
-        break;
-    case ProtocolError:
-        state = xState::Connecting;
-        ReportError(ErrorCode::PROTOCOL_ERROR, ErrorSourcePrinter);
-        break;
-    case VersionMismatch:
-        StopKeepPowered();
-        ReportError(ErrorCode::VERSION_MISMATCH, ErrorSourcePrinter);
-        break;
     case ButtonPushed:
         lastButton = logic.Button();
         LogEchoEvent_P(PSTR("MMU Button pushed"));
         CheckUserInput(); // Process the button immediately
         break;
     default:
-        break;
+        if(reportErrors) {
+            switch (ss)
+            {
+            case CommandError:
+                ReportError(logic.Error(), ErrorSourceMMU);
+                break;
+            case CommunicationTimeout:
+                state = xState::Connecting;
+                ReportError(ErrorCode::MMU_NOT_RESPONDING, ErrorSourcePrinter);
+                break;
+            case ProtocolError:
+                state = xState::Connecting;
+                ReportError(ErrorCode::PROTOCOL_ERROR, ErrorSourcePrinter);
+                break;
+            case VersionMismatch:
+                StopKeepPowered();
+                ReportError(ErrorCode::VERSION_MISMATCH, ErrorSourcePrinter);
+                break;
+            default:
+                break;
+            }
+        }
     }
-    
+
     if( logic.Running() ){
         state = xState::Active;
     }

Firmware/mmu2.h

@@ -226,11 +226,17 @@ private:
     /// Along with the mmu_loop method, this loops until a response from the MMU is received and acts upon.
     /// In case of an error, it parks the print head and turns off nozzle heating
     void manage_response(const bool move_axes, const bool turn_off_nozzle);
-    
-    /// Performs one step of the protocol logic state machine 
+
+    /// The inner private implementation of mmu_loop()
+    /// which is NOT (!!!) recursion-guarded. Use caution - but we do need it during waiting for hotend resume to keep comms alive!
+    /// @param reportErrors true if Errors should raise MMU Error screen, false otherwise
+    void mmu_loop_inner(bool reportErrors);
+
+    /// Performs one step of the protocol logic state machine
     /// and reports progress and errors if needed to attached ExtUIs.
     /// Updates the global state of MMU (Active/Connecting/Stopped) at runtime, see @ref State
-    StepStatus LogicStep();
+    /// @param reportErrors true if Errors should raise MMU Error screen, false otherwise
+    StepStatus LogicStep(bool reportErrors);
     
     void filament_ramming();
     void execute_extruder_sequence(const E_Step *sequence, uint8_t steps);