Syntax highlight getting lost when jumping down large file

I am writing a book using Asciidoc format. You can find the Asciidoc file here:https://github.com/krlawrence/graph/tree/master/book

I am using MacVim version: 8.0.1420

I have not noticed this problem as much in earlier versions of MacVim and it is not an issue editing the same file on Windows using Gvim.

If I load the file and set the syntax to Asciidoc the highlighting looks fine. However if I then do a search that requires jumping way down the file or if I just manually jump to the end of the file, syntax highlighting is lost. Doing a syntax sync fromstart does not bring it back and setting the syntax back to Asciidoc again only seems to work if I jump back to the top of the file and manually scroll down the file. As soon as I jump down the file again same problem. This seems to have started happening since I updated to this version of MacVim.

My OS is MacOS 10.13.3

I have sometimes seen this behaviour before but never until now encountered a case where doing a syntax sync fromstart does not fix it.

まず、macOS 上の MacVim 8.0.1420 を使い、リンクされた book ディレクトリ内の Asciidoc ファイルで報告内容を再現します。Asciidoc の読み込み、末尾へのジャンプ、syntax sync fromstart の実行、先頭からのスクロール後の構文ハイライトを比較します。大きくジャンプした後もハイライトが正しい状態を保ち、報告された同期コマンドが期待どおりに動作すれば完了です。