SPI is not thread safe, and causes problems on Gen 3 devices using the Ethernet FeatherWing. A fix is planned, but has not been implemented.
The Photon/P0 don’t use SPI to communicate with the WiFi radio, however. They use SDIO to the BCM43362.
Your symptoms do sound like a thread safety issue, so there very well may be one in something else other than SPI. It’s also possible that the STM32 SPI and SDIO interfaces share resources in some way.
