add_posted_to_filter=ON fails occasionally

Moin moin,

with
	tin 1.9.2
	add_posted_to_filter=ON
	default_filter_select_header=0
I noticed that some of my posts cause followups within
default_filter_days (actually within 2-3 days of 30) to highlight,
while with others sometimes it fails.
 What else can have an effect on this so it works for all of my
posts?

-- 
© Rado S. -- You must provide YOUR effort for your goal!
EVERY effort counts: at least to show your attitude.
You're responsible for ALL you do: you get what you give.