To those already doing the course, frustration and pain are natural learning phases to anything and it is no different with OSCP. You can either throw your hands in the air and give up or TRY HARDER and eventually succeed. Knowing that the machines in the labs are vulnerable but there is just something you do not see can cause a bit of discomfort. Keep looking, be like a detective gathering clues and connecting the dots. Ask people, read books on the subject, use google, do your research because the problem you faced was probably tackled by somebody else in the past. Keep notes and do not forget to do the root dance once you are in:).