Cursor Based Incremental API 504 Issue

Hey everyone,

I'm pretty new to using the Zendesk API/forum, so apologies in advance if this question has already been answered or needed to posted elsewhere. We have been trying to load all ticketing data and have been utilizing the recommended cursor based incremental export to do so. The data was initially being loaded from 1200 days ago and seemed to work fine with a few 504 errors at times (the build in retry would handle these instances). At a certain point, we started only receiving 504 errors and I've tried to restart the process where it left off by utilizing the "start_time" parameter again instead of the last cursor saved with no luck. We have another script/process that loads the latest tickets using the same method and it seems to be successful. Could anyone assist me with understanding what the error is? 

Endpoint example: