Tree preservation zone

There is a problem

1000 entries with tree-preservation-order field must match the reference field in the tree preservation order dataset

reference: TPO438
name: 20/1987
tree-preservation-order: undefined
20/1987
tree-preservation-zone-type: group
geometry: MULTIPOLYGON (((0.667156 51.283897,0.669523 51.282742,0.669562 51.282745,0.669594 51.282732,0.669600 51.282708,0.669792 51.282606,0.669848 51.282535,0.670161 51.282201,0.670240 51.282129,0.670278 51.282146,0.670436 51.282292,0.670454 51.282341,0.670488 51.282392,0.670506 51.282495,0.670429 51.282676,0.670317 51.282721,0.669940 51.282749,0.669728 51.282795,0.669191 51.283083,0.669051 51.283171,0.668601 51.283416,0.668409 51.283566,0.668253 51.283668,0.667968 51.283824,0.667695 51.283930,0.667560 51.283966,0.667264 51.283980,0.667200 51.283965,0.667173 51.283943,0.667156 51.283897)))
point: POINT (0.668971 51.283118)
notes: The Maidstone Borough Council Tree Preservation Order No 20 of 1987 under Section 60 of the Town and Country Planning Act 1971 Group of Trees - G9 comprising Ash, Sweet
organisation
entry-date: 1987-07-14
start-date: 1987-07-09
end-date

Your dataset is missing the tree-preservation-order column.

The Tree preservation zone guidance explains how to fix the issue:

The reference for the tree preservation order that covers this zone.