Some patterns of banners don't apply correctly on shields

When I craft a banner, there's no problem, but when I merge this with a shield, the shield will change sometimes the banner.

What I expected to happen was...
The banner apply correctly on shield

What actually happened was...
The banner change a little once merged with the shield

Steps to Reproduce:

Test this craft of banner (Tardis) => https://minecraft.tools/fr/banner.php?color_id_0=4&shape_id_1=28&color_id_1=15&shape_id_2=37&color_id_2=4&shape_id_3=14&color_id_3=0&shape_id_4=14&color_id_4=4&shape_id_5=26&color_id_5=0&shape_id_6=26&color_id_6=4#crafting

Or this one (England's Flag) =>
https://minecraft.tools/fr/banner.php?color_id_0=4&shape_id_1=16&color_id_1=15&shape_id_2=15&color_id_2=15&shape_id_3=17&color_id_3=1&shape_id_4=11&color_id_4=15&shape_id_5=13&color_id_5=15&shape_id_6=14&color_id_6=1#crafting

Or this one (Klaws) =>
https://minecraft.tools/fr/banner.php?color_id_0=4&shape_id_1=36&color_id_1=1&shape_id_2=27&color_id_2=15&shape_id_3=26&color_id_3=15&shape_id_4=24&color_id_4=15&shape_id_5=23&color_id_5=15#crafting