Ominous banners from version 1.14.1 won't stack with ones from 1.14.2 Pre-release 1
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[media][media]
This sounds a lot like MC-151793
Seems like 1.14.2 banners stack with 1.14 ones, as the extra tag was removed. Hm... it's unclear whether banners from either version are supposed to upgrade themselves.
Merged into MC-151793