When connecting the panels, it is best to proceed as follows.
Hold the panel to be connected at a slight slant. You can hook the panel while the groove is already partly in the tongue. Then lower the panel and push the seam together (with the foot). In judo terms, you would do a ‘De-ashi-barai’ (lateral foot sweep)
If a panel does not fully connect at the top, you can push the hook a little to the side for a tighter connection.