BigAntStudios
Premiership Player
I'm sure BigAntStudios will be able to provide far more than I can but...
Bugs will be ranked on some sort of scale depending on how game-breaking they are. Do they stop progression in the game (e.g. a crash)? Does the AI somehow break the rules (e.g. out of bounds called when the ball goes through for a goal)? And so on. All bugs are also ranked on how easy they are to fix. Something like the BOMBRES error is probably a really easy fix. These are then worked towards a deadline so some bigger bugs (like trading bugs) may be really hard to fix so won't make the next patch but something that seems insignificant (BOMBRES) gets fixed. This causes the masses to scream "Why did you fix the spelling of BOMBERS when it means nothing to gameplay but left me with players smothering a set shot???"
Killing bugs is a fine art. Not every bug will be killed and bugs will arise from the patches. There's no doubt about that. It's a matter of minimising what you can and hopefully taking out game-breakers and possibly living with the cosmetic bugs.
I'm sure every Studio have their own way of labelling things, we have "Must Fix", "A", "B", "C" - where you'd like to clear all M, A, B and most C. M's are crashes, non-progression errors and the like, A's are things that greatly limit the experience, B's limit the experience, C's are things like wrong colours, the spelling issue pointed out above, etc.
Each Studio/Publisher has their own take on Patches, I'm not letting out any secrets when I say that Sebastian Giompaolo hates patches, it's plain to see from the number of patches his games get.
We have an alternate take on that, we will patch often, we won't wait for the B/C bugs, we'll patch as soon as there are M or A's fixed, best and most extreme example would be AO Tennis with a patch on average every 5 days for 6 months (we also added a lot of content with those patches and new gameplay).
The PS4 and Xbox platforms can patch within 24-48 hours from submission, IMO there is no good reason to make people wait. Nintendo patches are a pain, the fastest we can get the simplest of patches through is weeks. e.g. We just released a patch for AO2 on Switch that was available on PS4/Xbox AO2 weeks ago.
Any dates given or deadlines for patches are entirely arbitrary and set by the publisher, not the platform holders.