i've moved mine two times, no problem. no tricks.

what was wrong about your spot? they are pretty adaptable plants. seem to take all sorts of light conditions. is it your soil? i only have experience with them in sandy/silty soils...

Established Mahonias tend not to come with a good ball and may dry up after transplanting.

Being half Mahonia lomariifolia this and other selections in the cross may respond markedly to warm planting sites here, and are definitely not as cold tolerant as M. japonica.

I moved an established M. japonica last year and got the impression that if I had not really poured on the water for some time afterward it might have gone brown. Of course, if there is too much root loss a shrub browns out whether you water the soil or not - the problem is water transpired through the leaves not being replaced by the missing roots. You have to treat such a transplant as a cutting, keep the top moist in order to have success.