Hi @dicky,
Judging from the error, It looks like the device was shut down right at the finish of the compression progress, which caused this error. But you can send us a Full System report at support@emlid.com, and we will double-check.
To ensure that this issue won’t happen in the future, we have released an update (32 Beta version 1), and in this version, the compression should be finished correctly even if the device is shutting down at the same time. Ultimately, this will be part of the stable version as well.
My suggestion is to perform the survey again and check the Logging tab to see if your logs are completely compressed and saved on your Reach after you stop logging.