Outlook Rules problem

[Geoff]

I have set up a couple of basic rules to screen and move
incoming mail to other folders on my pc. The rules work
fine most of the time and the logic seems ok but every so
often messages which should have been moved stay in the
inbox, BUT when I re-run the rules manually with "run
now", the emails ARE moved, suggesting that the rules
themselves are OK! This behaviour is unpredictable. Does
anyone have any suggestions?
Many thanks
Geoff
Sussex
UK