When placing the decal around this object it gets distorted at the back. The object is the from the starter assets. I've tried 'Generate UV' and that doesnt help. How can I fix this? I've attached an image below for ease of reference.
What are you steps? Can you describe how you placing decal and what are your decal properties. Also sharing file can help to understand problem
I selected the jar and placed the graphic using "Place the graphic Model". Where should I send the file? Tried attaching the dimensions file and I get an error saying the content type does not match its file extension.
to share a Dn file in Adobe cloud you must zip it first... this is because Adobe uses the buddle system and library team doesn't talk to Dimension or bother to test things actually work in the real world before kicking them out the door in time for Max
note only zip is allowed not any of the other standard files types like 7z
decal can not ever go all the way around an object... that needs a fill instead
I get error "The file type (.zip) is not supported."
it is supported if you use the file sync system, not the library
open the local storage to add your zip file 
then once it uploads open the web storage  to share the zip
Thank you for sending file. I think this is a very bad bug that do not allows to place image on sphere object. I try on cube and it work fine but small gap still happens between edges.If you will change your jar form to square it will work fine.
Here is a capture of my simple model with decal that I have created for testing.
I will report this to Dimension Team, today and will inform you about their feedback.
Thank you. I hope they find a fix soon.
Thank you @Ussnorway. I appreciate all the work you put in to find a work around. I'll use this in the meantime until Adobe finds a fix.
np but shop around as well... a quick look on Adobe Stock could save you a lot of time