The drag selection is enabled immediately after dragging the cursor a little (1-2px). This causes issues when a row is expanded/collapsed first then clicking the checkbox as sometimes, the cursor is dragged in the checkbox. Then drag selection resets the previously selected rows. Here is a screencast of the issue:

https://screenrec.com/share/y6pPGWjUZH

1. Expand a row
2. Click and drag the cursor in the checkbox (1-2px)

https://stackblitz.com/edit/angular-qnaphv-2nszye

The drag selection should not be enabled.

The Grid has a logic for enabling the drag selection after N-pixels of dragging. Could be reused in TreeList as well.