GRM references Octokit 10.0.0 which has known bugs regarding int vs long. We should upgrade to Octokit 12.0.0 which resolves some of these bugs (such as octokit/octokit.net#2928 for instance).
BTW: my guess is that more of these int vs long issues will be discovered and solved in the near future so I wouldn't be surprised if we had to upgrade again in the future.
Here's an example demonstrating that my build is failing due to this issue:
https://ci.appveyor.com/project/Jericho/stronggrid/builds/50054134/job/k3i5irek8a2bsa33#L487