What you describe is a group of relatively advanced learners who have adopted a certain type of errors by habit. That advanced learners dislike drills and similar types of activities is also clear - it is something that is not appropriate according to their current skill level, and very often, it is boring for them, too.

I think that what is needed a type of learning activities that suits their needs. For that, you should use some authentic language material at their skill level and embed that in some more complex communicative activities - begin with listening/reading comprehension in the first stage, and only later move on to a stage where productive activities (speaking/writing) play an important role.

Use worksheets and texts dealing with the kind of error topic that your learners have!

And, by all means, avoid drills - this could really discourage your learners!

Good luck!