1) Hesitation fillers that show struggle.
These are often in the form of uhhh, uhh or hmmm, errrr, etc. The reason they occur is often merely that the language has not caught up with the thought. If it were your 1st language that brain can access the words automatically since the connection to memory is very well refined.
The best way to deal with these is to recognize that you are doing it a lot and try to employ different strategies. I suggest that you merely pause to think and, if you must fill in, do it with 'thinking fillers' such as "Well,....Let me think,....That's a good question,......I will talk in a further post about the pause and string technique which allows better pacing. In general, pausing can be a very good strategy for letting the language catch up with the thoughts.
This often occurs with band level 5.5-6.0 candidates. Essentially the candidate repeats many phrases (eg " So the main, the main, the main problem is, is,is that....). Instead of the uhhh, uhhh, the candidate fills in by using the same word again. This shows to an examiner that the candidate is struggling with the sentence and because it affects the speakers smoothness, it can affect the fluency mark.
The best advice is to again, as mentioned above, try to have more productive fillers and to make sure the thought is completed before moving on with the words. It sure makes a big difference when someone points out to you when you are doing it.
We can get very stubborn when trying to communicate and we want the right words to communicate our thought. What can happen is that a candidate can get stuck trying to remember a word. In the meantime, a lot of struggle signs appear on your face which again affects an examiner's impression of your control and confidence in the language.
The preventative advice I would give is not to trap yourself into it. In other words, do not make your thoughts too complex for this exam because you may find yourself having difficulty communicating. It is best sometimes to simplify your thoughts and emphasize the language you know so well already. If you are stuck on a word, do what people do in traffic with their cars. Simply go around the word and use a simpler word or expression. Its perfectly ok to exit a train of thought and even tell the examiner you want to explain it in a different way. In other words, exit a struggle situation fast.