Using the standalone version for debugging is not recommended since the very large source will have to be loaded and parsed by the debugger. It's much more efficient to debug using the developer version.
If you suspect an issue in the object serializer classes, then be sure to disable parallel processing in the abapGit settings. Otherwise, the debugger will not stop at your break-points.
In case you can't resolve or pinpoint the issue, try to reproduce it using a case from the abapGit-test organization. If you don't find a test case, open an issue and we will create a new repo for it.
Also, the lower right corner of the HTML output will NOT show "JS OK". Troubleshooting depends on the type of SAP GUI you are using.
Check SAP GUI Setup for known issues related to SAP GUI.
SAP GUI for Windows
If you are using SAP GUI 7.6 or below, or SAP GUI 7.7 with Internet Explorer control, then follow these instructions on how to use the IE Debugger in abapGit:
If you are using SAP GUI 7.7 with Edge (Chrome) control, use the developer tools that come with WebView2:
SAP GUI for HTML (Web)
Troubleshooting depends on the type of browser you are using.
SAP GUI for Java
Running abapGit completely in a browser is still a proof-of-concept. Open an issue here.