The issue with instanceof only occurs when using Svelte Headless Table plugins.
To visualize the issue, follow the instructions:
Go to node_modules/svelte-headless-table/plugins/addSortBy.js
After line 131, add the following:
console.log('toggling');
console.log(cell);
console.log(DataHeaderCell);
console.log(cell instanceof DataHeaderCell);
With yarn dev, cell instanceof DataHeaderCell returns false.
With yarn build && yarn preview, cell instanceof DataHeaderCEll returns true.
