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.

首先，使用 macOS 上的 MacVim 8.0.1420，通过链接的书籍目录中的 Asciidoc 文件重现该报告。比较加载 Asciidoc、跳转到末尾、运行 syntax sync fromstart 以及从顶部滚动后的语法高亮。完成的标准是：在大幅跳转后高亮仍保持正确，并且报告中的同步命令按预期工作。