When attempting to migrate a list, the following message is displayed:
The column ordering for the list could not be reproduced at the destination.
Sharegate was unable to set the column order on the destination list, which could result in the columns being in a different order in the destination list when compared to the source list.
This problem normally occurs because the page for editing the list's column order is not a standard one. One possible cause can be that you use a farm solution for customized global navigation (or similar layout changes).
The most straightforward solution is to reorder your columns manually in the destination list after the copy.
If you have many lists with this issue, in which you need to preserve column ordering, you can instead investigate your farm solution to ensure that everything in your configuration (web.config) is functional. As a last resort, you could disable the custom solution that changes the navigation or the layout during the migration.