High-bypass turbofans are finicky things. It seems likely there will be more teething problems in that area. The GE-9x increases the bypass ratio by 11% from 9 to 10 over the GE-90 based on comparison of specs published in wikipedia. [1,2]
So the interesting question for launch is what else pops up.
[1] https://en.wikipedia.org/wiki/General_Electric_GE9X
[2] https://en.wikipedia.org/wiki/General_Electric_GE90#Specific...
