IMO this whole "detergent" thing is dreamed up theoretical nonesense which has snowballed out of all controll from this forum!
Any detergent will clean off right away & is not the cause of problems regarding spotting, streaks etc.
I have many situations on my round where I may trad one month & wfp the next! Yep, no "detergent" probs what so ever. Even when I used to use fairy!
There could be many factors- buid up of crap in seal, oxidised paint/stain/varnish/aluminium/pvc etc. A cut/tear/joint in the seal which holds dirt. If you clean the top frame it could be vents but the frame at some point will meet mortar/brick or stone, this will always have dirt on it just ready to mix with your pure & run down the glass! Unintentional maybe, you've flicked water above the frame with your brush? Either way, I would forget about detergent, your barking up the wrong tree & doing yourself no favours with your diagnostics of the real problem!