Is there any other API being called in AppInstall callback? I faced this error recently where this error occurred due to missing “Content-type” header in my third party API request in AppInstall callback.
Also call renderData() in both success and failure functions of $schedule.delete() or/and $schedule.create() and try passing the error code to renderData(), this will help in identifying where exactly the issue is occurring.
There were some platform updates that took place on the day of the reported issue, could you please check this again and let us know if the issue still persists?
It’s highly likely that one of the steps before renderData() is failing, maybe you can try calling the renderData() without any arguments and upload it as a custom app and check if the app gets installed, if the app get’s installed successfully you can backtrack from that point to check which of the steps are failing before the renderData() is invoked.
if possible please share the snippet or a screenshot of the onAppInstall event handler.