Adding headers via filters

Hi,

I have a couple of filters that add a header line to treated messages. That doesn't work reliably, I have a vague impression that KMail has to be idle otherwise for this feature to work (= applying the filter manually and waiting for it to complete). It could also have to to with the header caching in the akonadi db.

I observe this with 4.13 and 4.14, has this improved in more recent releases?

Thanks,
R.