We recently added support for renaming a file while doing incremental backups. That involved tracking in the checkpoint metadata whether a table had been renamed.
The code added assumes that the rename field was present in the checkpoint metadata, and if it isn't can return a WT_NOTFOUND unexpectedly from the __ckpt_load_blk_mods function.
We should update the code to handle the case where the rename string is missing from the config string.