The fact that only a few people are noticing this suggests that it’s specific to certain Android versions. For me, it works fine on 4.1.2 (API 16) and 4.4.2 (API 19) but fails to resume on 4.2.1 (API 17).
I may just end up releasing anyway and it will hopefully be fixed in the next stable release of MonoGame, Android development is very very frustrating