I think it's OK to work AND claim (self employed). I think it's about how much you have worked over the last 3 months. I have had on average about 4 hours work per week over the last 3 months (as opposed to 40 hours) so I have definitely been 'adversely affected' and have made a claim. If I had been working a much larger percentage of my normal hours I would not have claimed (although I'm sure I would have been tempted briefly).
It's a difficult one, as even if you only lost a day or 2 of work over the 3 months I guess you have been 'adversely affected', although I think that is just semantics and 'looking for loopholes' which is not a positive, morally correct or responsible way of dealing with this situation.