I've forgotten how many times I've heard "just a few lines of code", the phrase always makes the heart sink and the worry levels rise, and it is never uttered by people who actually realise the risk involved. Note that I say that having spent most of my software career outside of safety-critical and/or aviation work.
Software is easy to change, that is (one of) its strength. It's Achilles heel is that is is too damn easy to change and change requires far less thought than it should. Just because you can does not mean you should - but management will always ask if you can, and then tell you that therefore you should.
It is a whole different game coding in a safety related environment. I have worked in maintenance areas where "just changing a comment will take 18 months" This has the contrary effect of urgent fixes having to be patched into systems without the 18month wait if the world ends if they cannot keep operating.
I would suspect that the Max software has a very concentrated team working on it and that the fix itself is 'just a few lines of code' and was completed a month after the first crash. The rest of the time is QA, testing, documentation and certification. The 'delay' may well be the effect on code certification of the spotlight on the process due to the second crash. The work will now be to rule therefore be very slow.