Thanks for the suggestion, it was super helpful to have had 24 hours rest, and to take a fresh look at this thing. In the end the change was easy. Assigning slot_config.gpio_cs and/or slot_config.gpio_cd cause the issue. Removing those lines and allowing them to keep the value from SDSPI_SLOT_CONFIG...

Dear Forum, I hope this isn't a re-post, the search feature did not work well with "sd" as a search term. I am trying to interface a Sparkfun ESP32 thing with their ESP32 Thing Motion Shield to use SPI SD access. - https://learn.sparkfun.com/tutorials/esp32-thing-hookup-guide - https://learn.sparkfu...