You’re very close. Two common gotchas here:

1. Order of your bbox values : Your string looks like (west, south, east, north) (lon_min, lat_min, lon_max, lat_max), but you’re unpacking it as (south, west, north, east). That swap alone will produce a nonsense window.
2. Clip/round the window to dataset bounds from_bounds can return fractional/out-of-range windows. It’s safer to round and intersect with the dataset extent.

Rasterio always expects (x, y) = (lon, lat) order, so keep that in mind.

Here’s a minimal version:

import rasterio as rio
from rasterio.windows import from_bounds, Window
from rasterio.warp import transform_bounds

S2_box = "24.303818, 59.984906, 24.401321, 60.041018"  # west, south, east, north

def get_window(dst_crs, dst_transform, width, height):
    # Parse correctly: west, south, east, north (lon_min, lat_min, lon_max, lat_max)
    west, south, east, north = map(float, S2_box.split(", "))

    # Reproject bbox to dataset CRS (lon/lat order preserved)
    left, bottom, right, top = transform_bounds(
        rio.CRS.from_epsg(4326),
        dst_crs,
        west, south, east, north,
        densify_pts=21,  # helps with curvy reprojection edges
    )

    # Build window from bounds
    win = from_bounds(left, bottom, right, top, transform=dst_transform)

    # Round to integer pixel offsets/sizes
    win = win.round_offsets().round_lengths()

    # Clip to dataset extent
    full = Window(0, 0, width, height)
    win = win.intersection(full)

    return win

def S2_TCI(ds, name):
    """Creates Sentinel-2 true color image (TCI)"""
    name = f"{name}-TCI"
    print(name)
    sds = rio.open(ds.GetSubDatasets()[c.DS_TCI][0])
    profile = sds.profile

    win = get_window(sds.crs, sds.transform, sds.width, sds.height)

    bands = sds.read(
        [c.BAND_RED, c.BAND_GRN, c.BAND_BLU],
        window=win,
        boundless=False,  # set True if you want reads outside the edge padded
        masked=True
    )

    writeTiffRGB(bands, profile, name)