I have the same issue, and also use the Co-Authors Plus plugin, so that seems like the likely culprit.
It seems like a user object is returned somewhere instead of just a string with the name, if I’m interpreting this correctly.
<b>Fatal error</b>: Uncaught exception 'InvalidArgumentException' with message 'Method expects this value
----[
object(stdClass)#3798 (9) {
["ID"]=>
int(41)
["display_name"]=>
string(12) "Test"
["first_name"]=>
string(12) "Test"
["last_name"]=>
string(0) ""
["user_login"]=>
string(11) "Test"
["user_nicename"]=>
string(11) "Test"
["user_email"]=>
string(21) "[email protected]"
["user_url"]=>
string(0) ""
["bio"]=>
string(0) ""
}
]----
to be one of the types
====[
string(40) "Facebook\InstantArticles\Elements\Author"
]===='
