This is a macOS10.13 issue, specific for some Intel GPU cards. Apple has fixed(partially) this issue inside macOS10.13.4 released build.
Following are the workaround for resolving this issue.
1) Update your mac machine to latest macOS10.13.4. Here, Apple has fixed this issue to some extent. You will face very less number of rendering issues.
2) Disable GPU preview and set display performance as typical.
Once you have updated to macOS10.13.4 .You might still face some rendering issues. Since, Apple has not fixed this issue completely.
Please switch off GPU rendering for these cases and report a separate post for tracking.Paul Koch commented
Regularly I get grey triangles in my Indesign files, which will go away after I make a small change or move my cursor. This is only in Indesign.
Using MacOS High Sierra with Indesign CC 2018 on a new Macbook Pro with two screens. (also happening on just the macbook screen)
It doesn't affect the file and the triangles are not physically present.Paul Koch supported this idea ·