Systematic debugging flaws probably; and lack of tooling to easily isolate.
Systematic flaws: a cross between groupthink, early flawed assumptions, deference to team leads, a 'I just look for 1hr, if I can't find move on' (which leads to not looking), or just plain simple "reading" instead of searching.
Lack of tooling: many game engines are infamous for lack of control over tooling. I havent used many, but I understand it would be quite an effort to run meaningful parameterised or structured fuzz testing on most systems. This makes it hard to artificially confirm suggestions. That said, there is practically no excuse for them not to just add a bunch of counters to the game - even on their internal testers it would very quickly become clear there was a bias.
Most of my 'should have caught it earlier bugs' are of the 'deference to lead' variety. I looked, didn't see immediately, handed off with some notes, and then the follow up debugger(s) took notes or thoughts as gospel. This is really hard to fight - I write something along the lines of "my hunch is there is a problem in code x because it handles y and is poorly structured/tested. I checked z and found i, j - queries as follows" and then find the debuggers effevtively refuse to look anywhere past x. This is particularly true for a group of debuggers, who play chinese whispers with groupthink and invent reasons it must be x.
Systematic flaws: a cross between groupthink, early flawed assumptions, deference to team leads, a 'I just look for 1hr, if I can't find move on' (which leads to not looking), or just plain simple "reading" instead of searching.
Lack of tooling: many game engines are infamous for lack of control over tooling. I havent used many, but I understand it would be quite an effort to run meaningful parameterised or structured fuzz testing on most systems. This makes it hard to artificially confirm suggestions. That said, there is practically no excuse for them not to just add a bunch of counters to the game - even on their internal testers it would very quickly become clear there was a bias.
Most of my 'should have caught it earlier bugs' are of the 'deference to lead' variety. I looked, didn't see immediately, handed off with some notes, and then the follow up debugger(s) took notes or thoughts as gospel. This is really hard to fight - I write something along the lines of "my hunch is there is a problem in code x because it handles y and is poorly structured/tested. I checked z and found i, j - queries as follows" and then find the debuggers effevtively refuse to look anywhere past x. This is particularly true for a group of debuggers, who play chinese whispers with groupthink and invent reasons it must be x.