I've noticed that when trying to select multiple takeoffs and you miss when you click (i.e. click a blank spot) while holding shift all selections are deselected. I've found this to be quite frustrating when attempting to select a few dozen takeoffs to convert or duplicate.
I've also noticed that when you shift click a single takeoff it does not deselect it, but if you 'green' lasso it, it will deselect it.
@Victor Sorry about the inconvenience here. I can see how this would be frustrating. Both of these are now fixed in local development, and will go out with the next release.