If this had happened from the very first filter wash, there could be a few possibilities.

The first is that the filter was defective and the slightest variation in dirt or moisture changed its composition. 

The second, which may not be as obvious is dependent on use and what is passing through the filter when vacuuming. Where in the example ultra fine dust, building material, saw dust and the sorts are vacuumed, some of this can be deposited inside the filter. Requiring you to do a thorough wash. 

May I suggest the next time you wash the filter, you dry it fully and then repeat the process. If this doesn’t resolve it in the long term, a replacement should rectify the issue. 

David. 

David,

Thank you for taking the trouble to respond.

However, the issue has only started after I had the machine for a couple of years and getting a new filter made no difference. In a sense it is a problem I can live with, but I would have liked to correct it if possible.

Is it a genuine filter? Some of the replicas are iffy. I’ve tried three cheaper knock offs, none of them worked with my v10. It just pulsed.

Sam wise,

That is a fair point. The replacement filter that I got was a third party one as original ones were out of stock everywhere at the time. I will try an original one and see if that makes any difference.

You might want to try sending it in to the Dyson service center in your area to do a deep cleaning.  I had this issue over a year ago where the filter notification kept coming up even after I washed/dried it.  After they did the deep clean including the filter, it went back to normal and only alerted the need to clean after a month or so of weekly use.  However, after a year, it started asking for filter cleaning while vacuuming right after the cleaning/drying cycle.  So I am contemplating now whether to send for deep clean again, or just upgrade to the latest model.  I’ve had the V11 for 4 years already.