My student has done academic IELTS and obtained the scores he needs (7.5 overall). The problem is his grammar is still very unnatural, both in speaking and writing, and he still wants lessons with me to improve this.

His main issues are use of articles, reference (clear pronouns and antecedents), subordinate/participle clauses and tenses.

He has a good intuition some of the time, but other times it's like he's trying a structure he has come across but gets it confused with something else. For example, he might use a present participle clause with improper syntax where he could have just used a present simple independent clause. Possibly he is confusing present participle clauses with present continuous while at the same time not recognising that he needs present simple instead of present continuous!

I have been giving him proofreading exercises full of his target errors, going over his own writing with him, revisiting sentence types (starting from basic SVO main clauses and going into more advanced structures), article use and tenses.

He has been immersed in academic English for some years now. He's too far past the basics to be relying on simple syntax or to need to keep going over it, but I'm finding it really hard to correct his errors in the more advanced structures he seems to gravitate towards.

Any ideas?