I read a good idea from Scott Adam's where he recommends we take the higher ground.
We don't discuss the details and point the finger, we take the issue up and Say
"Software development is difficult, these problems happen but we are going to work hard to get it working and create the functionality you need"
They can't complain about this because you are sharing the same goals, you are doing the actions they want but crucially you aren't getting stuck in the weeds of blame and details (which are most of the time irrelevant)
This is similar to Steve Jobs response to Iphone 4 and Attenna's not working.
Smart phones are difficult, problems happen like this but we just want to make are users happy.