Incompetent managers

Amazon loses some of their best talent due to incompetent managers that use their direct reports' accomplishments to stand on while climbing the ladder.  After they cement their promotion, they hide their own poor work quality by using the stack ranking system improperly by omitting data to put said employees on a PIP. Why? Because they don't want to share the credit with the person who actually deserves ALL of the credit!

The PIP is impossible to defend against even with real performance data because direct reports are excluded from that part of the process. No matter what data you show, you are told that the "real performance data" which you can't see says that you are failing.

Amazon has very high skills bar for engineers, but not so for managers. 

Hopefully, they will fix this before they run out of more good people.