Re: What to do when....
I advocate the use of a "position set". At the end of each nymph drift, as the bugs rise thru the water columns, I will put in a postion set. The timing is hard to explain, but you can see what I'm talking about on a youtube video I produced.
I estimate we pick up 25% of our fish on the position set. You lose contact with the indicator in that portion of the drift (swing). As the flies rise thru the columns it simulates bug emergence or triggers fish to eat because food is getting away. Either way, try to utilize it.