Many writers that care for their writing worry that they stray too strongly from the Canon characters. And that worry is understandable.

But, once again, if you write a AU, or the point of the fic is a different characterization for an already established character, it isn't that much of a worry. But if you write a continuation of something, yeah, then it becomes important. Again, just research the original material. Maybe see how character X reacts to situations, maybe even ones similar to what you want to write, in the Canon material. Keep it consistent.

But if your plot requires the character to have different traits, maybe the point, the theme of your fiction is the differences to the original characteristics, explain them. Why is the character how they are now? How does it affect their social interactions, the general plot? Do the reasons of their change affect the plot directly? Indirectly would be though the changed traits of the character. And again, you need to keep the different characterisation consistent.

Honestly, this topic is something I don't have to write much. Just avoid it, make sure you know the original traits well or when the changes are intentional, make them logical and explain the why.

Don't be afraid of ooc characters, unless it is important to the fic, just write the characters well.