Adding an attribute modifier to an armor piece cause it to not only lose all attributes but at the same time causes the slot description(Ex: When on body) to be deleted.
This got me wondering why so i went to test classic methods to add attributes using commands and I think I found the issue
the bug seems to occur because you are assignating a UUID from a string which gives you a UUID in Hyphenated hexadecimal representation (no idea why it was working before but now it is not but looks like a minecraft issue), I noticed that when you apply an attribute modifier using UUIDLeast UUIDMost cause the same issue of not only deleting all attributes but also removing the entire slot description
But when I used a UUID in integer-array format (UUID:[I; 1, 1 ,1 ,1]) the attributes where working perfectly fine. Without deleting the rest (using the command data modify , data merge removes other attributes), so maybe you should try and look if this is the main reason about why some attributes are deleted (minecraft items will always lose their attributes but this can be fixed adding them again since those values are known, this should not be the issue with modded items)
Adding an attribute modifier to an armor piece cause it to not only lose all attributes but at the same time causes the slot description(Ex: When on body) to be deleted. This got me wondering why so i went to test classic methods to add attributes using commands and I think I found the issue the bug seems to occur because you are assignating a UUID from a string which gives you a UUID in Hyphenated hexadecimal representation (no idea why it was working before but now it is not but looks like a minecraft issue), I noticed that when you apply an attribute modifier using UUIDLeast UUIDMost cause the same issue of not only deleting all attributes but also removing the entire slot description But when I used a UUID in integer-array format (UUID:[I; 1, 1 ,1 ,1]) the attributes where working perfectly fine. Without deleting the rest (using the command data modify , data merge removes other attributes), so maybe you should try and look if this is the main reason about why some attributes are deleted (minecraft items will always lose their attributes but this can be fixed adding them again since those values are known, this should not be the issue with modded items)