I would think becoming profficient at reflective practice takes time and effort. So my first barrier is time. I am constantly time poor especially with adding yet more into the non-contact part of my teaching.
Working mostly in isolation I would think my reflections might not be fuly rounded or correct. I have very little opportunity for peer review or collabroative discussion. So my second barrier is not fully understanding how to effectively reflect.
Naturally focussing on the things that went less well than anticipated might make reflecting a negative experience. So my third barrier is balance. Keeping a healthy balance focussing and reflecting efficiently on what went well amd could be furthe renhanced and modified not just on what went wrong.