I recently switched from using the internal solver to using the external solver. Things worked smoothly for a couple of hours and then the camera failed to read images:
2023-06-14T14:53:53: [ERROR] Exposure failed to parse raw image.
2023-06-14T14:53:53: [ERROR] Cannot unpack /tmp/indi_BXzM7r: Input/output error
2023-06-14T14:53:53: [ERROR] Error downloading image from camera: Unspecified error
I checked straage usage and discovered the /tmp directory was near full - 99%.
There were 50 or so fits images in the dir. I removed the older ones and capture was successful.
I conclude that the external solver is not removing images from tmp. This fills the dir and there is no space to support the image download.