dont soap right up to the edge of the frame,leave about 1/2inch between soap and frame,and a bit of dogear and your be ok,
and I bet after a few months there is a visible white line round the window
a lot if is do with angles, if you hold a squeegie with to shallow an angle i.e handle to close to the glass this will
there is about another million reason as well right enough, I couldn't really say without watching you to be honest
Take note of that advice, there's always a reason for it il name a few;
Too soapy
Too much water within the squegee needs banging off
Little bits on your blade.
Fanning too close to edge of soapmark.
I learnt the hard way through trial an error, I change my rubber every week as I do a lot of olden wooden frames etc and that wears them down quick.
I've been experimenting with amounts of fairy, the perfect amount iv found is very very little in the sun, bit more in winter.
And whoever said don't touch edges oh my god ull be left with a smear where ur blades half onthe water and half on dry.done it seen what it does from the inside and I won't be doing it again. I find it best to soap it all up, let it drip down A bit off top frame(can do frames in this time) detail one side and top corner before squeegeeing, then fan it down and pull off at bottom. I never detail the bottom frame unless the soap is littlerally an inch up the window.
Hope that helped a bit!!