I was using foliagetype node and hand painting (wasn’t actually using the procedural vegetation).I tried re-producing it myself and couldn’t on an empty scene,think its caused by the foliage settings I had originally set up when I was just going to populate the map procedurally.
When I set foliagetype node to default the problem doesn’t happen so maybe I just mixed the wrong values somewhere and it causes a problem when I using a bigger brush to paint them.