Im at a dead end...

Projects General Guidance
7

You can't do this

  while(!(t1_changed && t2_changed))

because both variables occupy two bytes and part of the value could be changed by the ISR while you are reading the values

Do it like this

if (t1_changed == true) {
  noInterrupts();
   t1Copy = t1;
   newT1Copy = true; // not sure if this is needed
   t1_changed =  false;
  interrupts();
}
if (t2_changed == true) {
  noInterrupts();
   t2Copy = t2;
   newT2Copy = true;
   t2_changed =  false;
  interrupts();
}

and then in the rest of your code use t1Copy and t2Copy

...R