This hapens when Ashes the values of a column in a given table to be strictly increasing. This can be the case for example when you import a monopile with nonlinear springs: the table will have two columns, one with displacements and one with loads, as exemplified in the image below:

For Ashes to be able to read an input file with such a table, the column with the displacements must contain strictly increasing values. In the present example, this is not the case (the value line 290 is lower than the one at line 289), so the error message will be triggered.

Note: the line number in the error message corresponds to the line in the input file where the table is called, not the line where the table has non-increasing values. In the present case, the error message points to line 233, which refers to the corresponding table, but the table is actually defined from line 284 to line 308.