Restrictions hierarchy issues

Im having restrictions issue, some of my users have access to pages that inherit restrictions that should have blocked them.

For example with the following hierarchy:
(g1,g2) (g1)
Page 1 – Page 1.1 – Page 1.1.1
– Page 1.1.2

Page 1 viewing is restricted to groups g1 & g2, one of his child pages Page 1.1 is restricted only to g1 so I would expect that his child pages Page 1.1.1 & Page 1.1.2 would be restricted only to g1, but it seems that they are accessible to g1 & g2.

This happened twice in the last few days and only after we upgraded to v5.4. I encountered this issue only with pages created after the upgrade but I can't recreate this issue deliberately.