That is not just an issue with Thor. Many MH manufacturers from about 2014 to 2017 were burnt by bad material from a supplier that no longer exists.
Many people on this forum, myself included, have replaced the captains chairs with new ones from
https://shop4seats.com/.
Their prices are reasonable and you get a much better product but they currently have a long lead time between order and fulfilment.
They also sell RV furniture and some have bought replacement couches and dinettes from them as well.