Just glancing at the error code it looks like you are putting less than / greater than brackets in the actual name (maybe that's just part of the error output syntax, not sure without opening up azuresets script and having a look). It then explicitly states than the "<" symbol IS the character that's unexpected. Assuming I'm not overlooking something, my guess is you need to not save set names with that.
If you already have set names saved that are in the XML and the file doesn't like it, you might have to delete the azuresets config file that gets generated and start saving sets fresh.
short version:
I think you are saving sets like this:
//asets save <SR>
and you should be saving sets like this:
//asets save SR
no brackets / quotation marks or anything that xml parsing would otherwise use.
P.S - I love the addon, but if I had one request it'd be to make the sets sort alphabetically when you use the list spell sets feature!