We welcome your feedback.
For the challenges to work well, it is important that the checkpoint locations are accurate so they can be detected by your GPS in the position you expect to find them. We try our hardest to place them accurately, but we may not always get it quite right. However, there is also the problem that the GPS on your phone may occasionally lose accuracy. If you fail to register a checkpoint, look at your trace on the results to see if it goes into the circle of the checkpoint in question. If it does there is possibly a location error.
If you think there is a placement problem, let us know the challenge name, the checkpoint number and your name so that we can look at the trace in the results. We will endeavour to test it and correct if necessary.
We are continually trying to increase the number of challenges available. If you would like a challenge in a new area, let us know. Postbox challenges are the easiest for us to produce although we are open to requests for other types.