Click a database name on the left. The list of tables expands as normal. Click a table name and it stays open.
But if you do certain actions on a table, the left pane keeps closing. When you click the table name in the breadcrumb at the top of the main panel.
One definite action to get this bug is to open a table in a new tab, i.e. right click on the table name in the left panel and click "open in new tab". But it also happened a few times in general use, possibly when running update/insert queries from the query box.