Hello,
If both devices PIDSA117 and PIDSA118 have the same product code (it can be checked in Status → Device window) and the same firmware version, there should not be any issues to upload configuration from PIDSA117 device to PIDSA118 via WebUI's System → Administration → Backup window.
If both parameters (product code and firmware version) are indeed the same, please clarify how are you downloading/uploading backup and provide the image of the error, if you're getting any.
Also, you mentioned that you're using uci export/import commands. Is it mandatory for you to use uci commands? Have you tried WebUI option?