Hello,
I think the authorKeywords and keywordsPlus are inversed, as on line 69-70 in tethne/readers/wos.py you have:
'ID': 'authorKeywords',
'DE': 'keywordsPlus',
while in the documentation of web of science (https://images.webofknowledge.com/images/help/WOS/hs_wos_fieldtags.html) it is written:
DE | Author Keywords
ID | Keywords Plus®