mine clearing not working

[medicff]

I am playing a generated campaign in 1965 and not only is the AI using many mines (saw other post) but I am unable to clear much at all. Using Mineroller tanks, CEV tanks, and multiple engineer units. Outside hex pointed in direction, inside hex, spotted mines (sometimes see on map when artillery or enemy runs into, but not spotted by my troops). No matter what I do , I have run many turns with engineers posed to clear and have only once clear a hex in this particular battle. Others have been fine. An Assault map default large. Thanks for any help. Save available upon request.