Fuel Injector o-rings keep breaking

So, a few weeks ago, I took out the fuel injectors to test the resistance as part of cylinder misfire troubleshooting. However, after putting it back together, I have had continuous problems with the fuel injector on cylinder four. The small rubber o-ring at the top of the fuel injector keeps tearing either after I put it in, or when I start the car (unsure). I have broken three or four o-rings trying to get this right. I have tried lubricating them and not lubricating them. I have done it as gently as I can. But I keep getting fuel gushing out as soon as I start the car, and when I take it apart again the o-ring is shredded. I did not have this problem with any of the others. Is there a special technique or something to make sure this does not happen? I was not able to find anything specifically about this elsewhere on the internet.