1. Export per project, not the whole workspace — most tools cap CSVs at a few thousand rows.
2. Open the CSV in a spreadsheet first — confirm the Title, Due, Priority columns look right. Fix any garbled rows.
3. Map columns on upload — the import wizard shows a preview. Don't skip it.
4. Notion: export as *Markdown & CSV*, then upload only the CSV.
5. Trello: JSON must be the *board* export, not a card export.
6. Still short? Re-run — imports are idempotent by title + due date, so duplicates won't stack.