ForAll Loops and Type Mismatches
There are always challenges when moving from something familiar to something similar but different. When you've been working with that "something familiar" for a very long time, some things become second nature. But when you move to "something similar but different", sooner or later you hit an error and become convinced it's not working like it used to. This is even more probable if enhancements mean you more frequently come across a specific paradigm. The rash developer starts throwing accusations, assuming they must be right because they have years of experience on their side. The wise developer double-checks first...and may find out that they were mistaken.