Can we get a closer look? Z-Bar flashing? Is the brick sill sealed (i.e. densifying agent)?

Is there a piece of stucco missing under the window? Stucco works great as a siding but the thing with stucco once water starts getting behind and stays wet it deteriorates and eventually falls off. I noticed a crack running from the left of the window down as another sign of a problem. Tap on the stucco someplace not under the window and it will sound solid and remember the sound. Next tap on the stucco under the window and if it sounds hollow it's separated from the lath and you have a bigger problem besides the improperly sealed window. Then tap to the left, right and down until it sounds solid again, this will be the portion witch will eventually need replaced.

Surprisingly and fortunately there's no hollow sound, the stucco itself seems to still be attached to the lath. What looked like a missing piece of stucco is just peeling paint. I know hairline cracks need to be repaired, but was planning to deal with that when the house is painted in a couple years. If you think it's more urgent than that I can look into it sooner, but since the moisture isn't following the crack I'm not sure it's the cause of this particular issue.

I've attached some more pictures per request, I just don't have a ladder for getting up top. Not sure exactly what is being looked for, I can't see any flashing on the finished window. It does appear everything visible is caulked shut. At this point, I'm suspecting the brick. I've only had the house for ~6 months, but never had it sealed. Considering the house had rotten exterior trim when I bought it, I doubt the previous owners had that attention to detail.

It's possible these windows aren't up to modern flashing expectations? It's a 1920s house and the replacement windows were installed probably 20-30 years ago.

On a side note since it's noticeable here, I'm already aware of the paint peeling from the trim, it's an adhesion issue with the Azek. I'm also aware you're not normally supposed to paint Azek dark colors, it's a special low-LRV paint. And since it's Azek, no risk of rot there.

Head trim should have had a drip cap with a kick out leg. Water running down the wall is settling on the brick sill. Brick sill needs to be tuck pointed and you should seal the mortar in this case to keep the absorbed water out of the stucco.

The guys who did the trim replacement pointed out that there was no drip cap to start with. They caulked the gap above the head trim shut in lieu of that. Sounds like this wasn't the best way to handle it, even if the Azek head trim won't rot from water presence.

I'll definitely get that brick done, seems necessary regardless of drip cap.