54 MHz Noise coupling into output

[Scott.Bonomi]

I am trying to connect a ESP32-U4WDH to a remote SPI Device using the interface called VSPI. Have t have a 3.3V VDIO because of the internal Flash.. In order to talk to a 1.8VDC device, have to pass all signals through a level shifter before reaching the target.
However I am getting a lot of 54 MHz noise on the lines. An "On" GPIO will show unacceptable amounts of noise while on, and go reasonably quiet when off.
The difference between the two scope screen shots is that in the noisy picture, the CS line was connected to the remote board. The wire run is about 15 inches. 1 M-Ohm probes an adding a common ground just added to the visible noise. We are seeing different levels of signal on different editions of our dev board. Not a kit, schematic is at
https://www.esp32.com/viewtopic.php?f=12&t=16867#p63749

I have ADC and DAC on, as well as WiFi as a master. Most of the GPiOs are in use, includeing trying to get GPIO15 (MTDO) as an output

[ESP_Sprite]

Hard to say, but 54MHz does not strike me as (an harmonic of) a clock that's used in the ESP32. Are you sure you don't have something else oscillating?