As a developer I get tons of people/clients delivering bugs/issues. There are some default things, every developer will ask you, right of the bat before he/she will even look at it.
Since I've been answering this question so many times already, I thought I'd write a short list of things every (proper) developer should ask so I can point people to it, instead of answering the question.
I'm a big fan of Timber, a Wordpress plugin which renders Symfony's templating language Twig into php code.
If you use Timber you can now render all your output in a Twig file, instead of having to echo the logic and all elements in a the (php) widget file, which makes for cleaner template files.
If you use the plugin Advanced Custom Fields a lot, like I do you're bound to run into some sort of limitation.
My problem (and so it seems, not just mine) was related to taxonomy and conditional logic. While building a site with profiles (with the use of an ACF form), I had a form where profile info had to be entered. For sex I had created a taxonomy, so I added it as a taxonomy field.