I cannot stress enough that in order to understand what might be going on you need to list the following things always -
Computer Platform (Mac or Windows)
OS
Version of Scaler
DAW
On my Mac OS 10.13.6 in Ableton Live I can right click - Choose Select All and it behaves as it’s supposed to. One work around would be to lasso all the chords you want to select.
New version of Scaler is due very soon so that might fix your issue.