Most accurate tool for generating tileset from raster

Question

I have been converting a raster consisting of 5m pixels to xyz tiles with PNG format in order to be consumed by Mapbox as a layer. I have been using gdal2tiles.py to achieve this and have been hosting them in S3, however I have noticed that there are some pixels missing when comparing the view on Mapbox compared to when viewing the raster in QGIS.

My process has been:

1. Apply qml style to raster in QGIS
2. Export raster as geotiff file from QGIS with the following settings

(compression was set to high and I removed the field: PREDICTOR=2

3. Run gdal2tiles.py like this:

gdal2tiles.py {file} --xyz --zoom=8-18 --processes={cores} --exclude

I put the above in because it could be something in my process that is causing the inaccuracies.

What is the most accurate way to generate a tileset from a raster file? I am curious about things like whether tms more accurate than xyz, or if there is a more accurate tool than gdal2tiles.py, or if I have done something to cause these inaccuracies myself.

Here are some images to illustrate:

The first picture is how it looks in Mapbox, the second in QGIS. You can see in QGIS there are 4 pixels up, whereas in Mapbox there are only 3.