It happens, I picked up a 3 pack of baby backs from costco 2 months ago, immediately put them in the freezer, and when I was ready for them, thawed in the refrigerator for 2 1/2 days.
When I opened the cryovac, the smell was very strong, even after rinsing and airing out. They were bad from the get go, but in the cryovac you can't tell.
a light sour smell that dissipates after rinsing is ok.
I once picked up a box of pork butts from a provisions guy that were bad, his guys tried to tell me it was my fault, until I stuck them with the thermometer. Still cold, just bad.
I will say, been around food purveyors for a long time, they hate to throw anything away, till it crawls off by itself,
![Big grin :D :D](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f600.png)
Most of the time it's good enough, but it pays to be vigilant.