<td class="prop"> <g:textField name="dimensions[${i}].value" value="${fieldValue(bean: q, field: 'value')}" /> </td>This is due to the construct [${i}], to resolve the problem wrap the i variable in braces [${(i)}]
<td class="prop"> <g:textField name="dimensions[${(i)}].value" value="${fieldValue(bean: q, field: 'value')}" /> </td>The error then disapears.