not sure if ive posted this once b4 or if anyone knows this, but when youve used a bit too many physics or glue or objects in one particular area, that space 'room complexity' becomes maxxed. you can select new objects ya wanna add, move them into position, press up, go to 'glue to object' and click on it, but dont glue, just hit B to back out and your object stays put. you can add much more this way and i havent found it to be laggy
Burn em down to rebuild em to burn em down again...