Damn, I didn't even think of that.
Can
@hoangvinhcbvn confirm whether the site was issued a penalty via Search Console before the sale was completed? Because it's possible that the site didn't get an official penalty, it just suffered a drop in rankings after the June 3rd core update.
It's still unclear to me whether @PassiveJournal intended to defraud the seller, or whether he bought a site, realized it was a bad investment and is now trying to recoup the cost through selling the Instagram account and guest posts. It's also possible that the site stats were not accurately represented during the sale.
Let's not jump to conclusions until @PassiveJournal has had a chance to reply.
Great news on the PayPal result!