The odd behaviour I reported is on the Galaxy S2 phone.
And up until now, I hadn't tried version 1.71 on the Tab. Now that I did try it, I find the Tab does not have this problem. Everything is as expected on the Tab.
>> If you click "all groups" twice, do you then see the correct phrases?
On the Galaxy S2 -
Tapping on "SHOW ALL" once (when a few other Groups are shown as selected, but not "SHOW ALL" itself) selects the "SHOW ALL" check-box correctly, as expected, greying out all the rest of the Groups, and all phrases are shown.
Repeating the tap on "SHOW ALL" (second tap) de-selects the "SHOW ALL" check-box, "un-greys" the rest of the Groups, and the phrases belonging to the previously selected Groups alone are shown.
As far as I can tell, the "SHOW ALL" check-box is behaving correctly even on the S2.
Also, on the S2, the phrases shown at any point in time is always the summation of the selected Groups, again, as expected. By selected, I mean the ones that actually have a tick-mark in the check-boxes against them.
The issue is only that, when I actually tap on the Groups, the check-boxes select themselves in a seemingly random fashion (not exactly random, but following the pattern I described previously).
So when I tap on a Group, the intended Group's check-box doesn't change state, but the check-box against the Group I had tapped just prior to the current one, does.