arena surface

I am on an almost perfect yard which I appreciate is a very rare thing and absolutely don't want to move. The only thing is the arena. It is a rubber/sand mix and is really deep and uneven, particularly now after very little rain for months. The horses are stumbling, tripping etc. A new surface...

apologies in advance, this may turn out a long post but we are at our whits end and Really not sure how to proceed.... 2 1/2 years ago we had Hymas arena install our arena at home. They came and did a site survey, quoted, I did the planning and then they constructed it, advised on maintenance...