The author, Reiji, is purposely keeping the manga in a cycle. He spent about 40 chapters making Kazuya grow out of his panic attacks only to quickly reintroduce them.
I wholeheartedly agree with you. You could really feel the push-pull from the author.
The last time I really read this manga was around the crowdfunding & film thing. You could really sense that "something" was about to materialize in the near future then.
But, now (after catching up), I could certainly feel that the author chose to backpedal. It's understandable though.
He simply went too far, especially with Chizuru. A resolution was just around the corner and yet he still needed more chapters (it's his source of income after all).
It's not that the author is using an unacceptable device: distance (not physical) & the doubt/anxiety that comes with it (or, like you said, the panic attacks LOL).
You could sense that the author is trying to make us think, "Perhaps, Chizuru is simply being grateful of Kazuya's kindness. She doesn't think of him in a romantic way.". But, at the same time, he also wants us to think, "Perhaps Chizuru just doesn't fully understand her feelings. She needs time to arrange her thoughts.".
It's totally acceptable for him to do so.
My only beef with the current state of affairs is how Chizuru's currently way beyond Kazuya's level. It feels way off balance.
In the last few chapters, Kazuya is the same as ever (or arguably, he's grown backwards) but we currently have way too many of Chizuru's awesome displays of maturity. Unlike 100 or 200 chapters ago.
Of course, it's undeniable that Kazuya gave things that Chizuru actually needed. But, with the current imbalance of character, the relationship simply feels like the great lady and her handyman. (Yes, I intentionally choose the word "handyman")
However, what truly fascinates me is the fact that this manga has plenty of hardcore fans. Just take a look at this comments (discussion) section.