Hi,
I'm not seeing any issues once I re-configure for SPI0. This included changing the SPI device number to 0, modifying the pin-mux accordingly, and most importantly making sure there are no conflicting switch settings that maybe clashing with the SPI0 signals.
In the project I sent last, there is a Readme_spi_slave_bf5xx.txt that documents the hardware settings. It was for SPI1. It says
SW2: 1(ON), 2(ON)
With SPI0 this setting will cause a conflict on SPI0SS. However your problem seems to be on MISO. I don't see this on my waveform, see attached image, all looks OK. ( yellow clk, purple MOSI, blue MISO, green SS). FYI, I'm using BF518 Ez-Kit (Rev 1.0, Rev BOM 1.6). The problem you are seeing seems to me to be hardware related and I cannot replicate it.