Corner 'Ears' on uPVC windows.

[cabinscooter]

This is a very minor problem but I'd appreciate some advice.
Within the last five years we've had most of our old timber windows and doors replaced in stages by a very capable chap. No issues with him, he always does a very good job and his attention to detail is of a high standard.
However, the 'filler'in the bottom corners of every window ( the window chap calls them ears) continues to dry up and fall out. When we got him back to replace first the timber front door (with a composite door) and then the uPVC back door, we pointed the problem out and he duly redid them. They are still coming loose. It's not worth getting him back for just this so I'd like to do something myself. I guess it's down to getting the mix right so that it adhered to the brickwork. I've attached a photo of a typical instance. I have some red mortar dye to match the brickwork . Any advice appreciated.

 

[foxhole]

The plastic moves in heat , filler should be left shy of the plastic by 4-5mm to allow for this .
Bit of a cardboard in there before filling and then when it’s gone off wet the cardboard so if can be removed .

 

[cabinscooter]

Thanks. So that's a gap of 4-5mm next to the plastic window. Can it go direct onto the brickwork? Can I use say, Sandtex masonry filler?

 

[Koolpc]

Flexible exterior filler would be what I would use....