Kindly check on description. On PayPal developer docs, this are the rules for description field

description string [1..127] characters

“The purchase description. The maximum length of the character is dependent on the type of characters used. The character length is specified assuming a US ASCII character. Depending on type of character; (e.g. accented character, Japanese characters) the number of characters that that can be specified as input might not equal the permissible max length.”

That means if you set a value in the description field it cannot be zero or exceed 127 characters otherwise it will throw that kind of error