Unable to generate stencil, check your stencil definition
This error occurs when the stencil to an operation could not be made valid.
Check if the stencil is generating a (schema) valid DOM. If it attempts to generate a structure disallowed by the schema, this error will be thrown.
Check if interpolated values are present in the operationData by the time the stencil is used. Remember only strings and the null value are valid attribute values. Numbers, objects or undefined are not.