That grant appears in your chain of title, correct?
Was the grant made by the person who sold the property to you? Perhaps they were in the same position as you.
Who installed the wall, and when? If, for example, the wall was standing in 1987, you have a plausible argument that the easement anticipated that the wall would be removed in association with the exercise of right to use the full width of the easement.
Is this residential property? Did you receive
this form or equivalent ("Does anybody other than yourself have a lease, easement or any other right to use or occupy any part of your property
other than those stated in documents available in the public record, such as rights to use a road or path or cut")?
Nobody reviewed a survey in association with the sale? Not even a mortgage survey? Nothing showed up when the title history was searched - and if not, why not?