The reason why the Mouse was not visible on my Mac after rendering was that the cursor was at some very odd position far far away from the actual MC window (in fullscreen).

To workaround this, set the Cursor Position to 0, 0 after playing a Camera Path. | https://trello.com/c/IHxYiBTE/

src/main/java/eu/crushedpixel/replaymod/replay/ReplayProcess.java

@@ -20,6 +20,7 @@ import net.minecraft.client.renderer.chunk.RenderChunk;
 import net.minecraft.client.resources.I18n;
 import net.minecraft.crash.CrashReport;
 import net.minecraft.util.ReportedException;
+import org.lwjgl.input.Mouse;
 
 import java.io.IOException;
 
@@ -133,6 +134,8 @@ public class ReplayProcess {
             ReplayMod.chatMessageHandler.addLocalizedChatMessage("replaymod.chat.pathinterrupted", ChatMessageType.INFORMATION);
         }
 
+        Mouse.setCursorPosition(0, 0);
+
         ReplayHandler.setInPath(false);
         ReplayMod.replaySender.setAsyncMode(true);