Someone in another town or country probably UK had a key to 5J. The key was not available to the PJ and GNR handlers. It was not available from MW or from OC or from any of the local property management companies. So they opened a window. Not rocket science, nor is 5A where it is obvious the person who opened the window did not have a door key that's why they intended to climb in a window instead. Same at 5G, and maybe at 4A and 5L also, no key so use window.
Hmmm. I can agree with some of that, but I have doubts about other bits.
The GNR didn't have a key available - ok and decided to go in through a window. Ok.
The police could have knocked the door out with an appropriate warrant, but they chose to go in in a less destructive way. Ok.
The GNR's immediate concern, bless them, was that she could have been in there as the dogs reacted.
However, I find it impossible to believe that no self-respecting PT burglar has worked out how to duplicate keys or pick bog standard locks.
It doesn't explain, eiher, why the PJ doesn't appear to have checked out why rotting food was there, nor whether that was the only explanation for the smell.
Perhaps the UK / PJ investigations now have done and have ruled it out... or not.