Inbox loses labels

I find the I use labels to filter my Next Action list. I have allocated labels to my Inbox to ensure I can see all Inbox items within each filtered Next Actions list. This works well until after a few days the Inbox “forgets” the labels allocated to it hence these items then disappear from my filtered Next Actions list. I am not sure what causes this but it is very annoying as I cannot guarantee that I will always see all of my Inbox items.

Any help much appreciated. Keep up the good work – the apps are getting better all the time.

Steve