Fragmentation on label decal

well i don't know what you did before but only why its not working now

I'd recommend you also have a look at this page https://helpx.adobe.com/dimension/using/whats-new/2020-2.html

with special interest in the 'Converting parametric models to standard models' section

I'm pointing this out because your 2nd screenshot is of a parametric model and if you don't convert it then that will cause a random Uv map to be included which is more likely to break up... to be clear, you will still need a 'fill' [not decal] to have a label where the edges touch each other around the fill 360* of any model but the end results will be much cleaner on a converted model

p.s, as a Mac user you may want to consider moving to Blender instead but good luck with it

why = because you are using a decal instead of a full

the fix is to change the graphic i.e, export and adjust in Photoshop

https://helpx.adobe.com/dimension/using/exporting-model-uvs.html