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: TPO171
name: 21/1987
tree-preservation-order: undefined
21/1987
tree-preservation-zone-type: group
geometry: MULTIPOLYGON (((0.679101 51.263420,0.678944 51.263470,0.678860 51.263471,0.678835 51.263452,0.678841 51.263434,0.678870 51.263402,0.678948 51.263333,0.679084 51.263271,0.679202 51.263204,0.679334 51.263106,0.679503 51.263015,0.679597 51.262952,0.679775 51.262852,0.679921 51.262774,0.680018 51.262747,0.680093 51.262703,0.680181 51.262623,0.680318 51.262547,0.680409 51.262522,0.680605 51.262501,0.680786 51.262529,0.680876 51.262577,0.680934 51.262630,0.680961 51.262671,0.680969 51.262726,0.680946 51.262815,0.680899 51.262855,0.680833 51.262888,0.680457 51.262989,0.680214 51.263035,0.679660 51.263249,0.679352 51.263331,0.679101 51.263420)))
point: POINT (0.680067 51.262928)
notes: The Maidstone Borough Council Tree Preservation Order No 21 of 1987 under Section 60 of the Town and Country Planning Act 1971 Group of Trees - G20 comprising
organisation
entry-date: 1987-07-31
start-date: 1987-07-30
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.