Cause of Error 000308: Invalid Field Type when batch running ArcPy script?

This is my first post on this site.

I am using ArcGIS 10.2 for Desktop.

I wrote a simple script in the form of a python toolbox to calculate the speed of travel between consecutive entries of a point shapefile. The script works perfectly on single files. However, as soon as I try to run it as a batch, I get an error:

Error 000308: Invalid Field Type.

EDIT: By running in batch, I mean I am right-clicking on the tool in ArcMap and selecting “batch”, and then loading in several shapefiles at once.

I suspect that the error comes from something about how I defined the parameters:

    inFileParam = arcpy.Parameter(
                             displayName="Input Feature",
                             name="in_feature",
                             datatype="GPFeatureLayer",
                             parameterType="Required",
                             direction="Input",
                             )

    indivName = arcpy.Parameter(
                             displayName="indivName",
                             name="indivName",
                             datatype="Field",
                             parameterType="Required",
                             direction="Input",
                             )
    indivName.parameterDependencies = [inFileParam.name]
    indivName.filter.list = ["Text"]

    dateField = arcpy.Parameter(
                             displayName="dateField",
                             name="dateField",
                             datatype="Field",
                             parameterType="Required",
                             direction="Input",
                             )
    dateField.parameterDependencies = [inFileParam.name]
    dateField.filter.list = ["Date"]

The indivName and dateField parameters are what gives the error when I click on the “check values” button in the batch window. Removing the filter seems to fix the error, but I would really like to have the filter. As I said above, it works just fine when I input them in a non-batch run of the tool. Also of note, this same problem has happened from pretty much every (but strangely not all) tools I have made.

As of now, my workaround is to modify the tool to explicitly code the field names when I need to do a batch run, but this is not ideal, since I am hoping to distribute this tool to other researchers.