Ominous banners not stacking

When I try to put my Ominous banners in a chest(I have 4 of them), they don't stack for some reason, they just stack for a split second, after that, part of the *Ominous banners* go to the other chest slot and the other part stays in the previous slot

What I expected to happen was...:
the Ominous banners shoud've stacked in one stack of 4

What actually happened was...:
they splitted in two different chest slots

Steps to Reproduce:
1. You put your Ominous banners on top of another stack of 1 and they dont stack

I suspect the issue beeing the minecraft version difference, when the server launched, it was in 1.14.2 in that version I got my first *Ominous banner,* after a while, the server updated to 1.14.3 and then I got the other 3 Ominous banners and since then they don't stack properly**