It runs into the above error when I clone the task or reset it.

from here:

AssertionError: ERROR: --resume checkpoint does not exist

I assume the "internal" code state changed, and now it is looking for a file that does not exist, how would your code state change, in other words why would it be looking for the file only when cloning? could it be you put the state on the Task, then you clone it (i.e. clone the exact same dict, and now the newly cloned Task "thinks" it resuming ?!)