Mineral oil is the only thing you should use on a butcher block. Think of the food you are eating- it gets a little bit of the wood finish on it. "Tung oil" products are usually varnish or oil/varnish blends (not actually tung oil). Pure tung oil is hard to find, and I doubt you are using pure tung oil. Either way, the problem is the "tung oil" finish is drying. You want a non-drying oil for the butcher block. Mineral oil is the best choice. The finish you used has already penetrated the wood and cured. That is why the additional coats look funny. Sanding will not remove it. Maybe someone else has an idea how to take it off so you can start over with mineral oil.

Actually I did use a pure tung oil (at least it was advertised that way) The whole thing feels dry and has set for 1 week but as I said the finish is variable.

Could it be that the butcherblock arrived from the manufacturer coasted with another finish which wasn't completely removed before applying the tung oil?

It came unfinished. I am kinda wondering if it sat in or got splashed with something that is making absorbtion uneven but we saw no discoloration on the box. Another source suggested maybe it was unevenly planed or sanded. When I looked at it it seemed level and even and we couldn't feel any differences in texture. Of course this was just with the naked eye.