Hi,
I am curious about the ‘short test’ you did: could you explain how it’s done? Normally if the controller loses power and restarts it will re-initialize SD card and detect the presence of SD card. This check is done only at the beginning when the firmware restarts, and is not done repeatedly while the controller is running. So I wonder if there is something specially with the duration of the power break that causes it to fail to detect the SD card.
The SD card status is indicated internally by the ‘has_sd’ variable. I don’t think it’s exposed to the web API, but this can be easily added. However, the key issue, I think, is the question above, because it shouldn’t lose SD card status in the first place.