The scaffold uses the Roo tag lib "form/fields/column.tagx" and "form/fields/table.tagx", which communicate with one another by passing comma delimited strings through request-scoped JSP variables.
Unfortunately, comma is not a safe delimiter in this context, as it can appear in the data (e.g. date formats can contain commas).
To reproduce this, try creating a scaffold for an entity with "MM" formatted dates, and viewing the list pages.
I have attached a fix as a patch (no unit test, sorry).
I tried to use NULL '\0' delimited strings, but I couldn't get JSP to accept \0 in a string. (Does anyone know where the JSP syntax is actually documented? I have been unable to find this out even after extensive googling.) So instead, I have used ✏, which seems unlikely to appear in any column headings or date formats.