As Vim has been my favorite text editor since around 2015 I really enjoy helping new users getting more comfortable with it and creating their config just the way they want. That's why I read and answered quite a few questions about Vim mappings. Eventually, I noticed some recurring patterns and decided that I wanted to address the most common errors. To do so I wrote a generic question on vi.stackexchange and tried to explain the root causes of the most common issues when one creates a mapping in vim.
It was fun to write but it is also pretty satisfying to see that this is my most read and upvoted answer! I believe that as long as new people will learn to use Vim these issues will still need to be addressed and I hope that what this post will do.
I think in the future I'll try to make an actual blog post about that maybe digging on more exotic edge cases.
But for now, this is a link I have sent to a lot a new vimmers and it seems to have been helpful to some of them: How to debug a mapping?