ESP8266 not worked in this configuration, because it radiates on nearby channels.
Data and power over USB only working good when clean power -- from OrangePi for example, another way there will be noise from USB line.
So better separate power from USB, what was before USB and ESP8266 was added in last moment and not tested.
So in FreeEEG32 alpha1.05 made changes that ESP8266 module was excluded, and UART isolator was not used, and only used power isolator for power supply from battery.
And SPI isolator was fixed so it can pass UART, so this isolated UART used to connect to external ESP32 devboard, to be used as USB when ESP32 disabled, or can be used as WiFi.
New changes will be tested in FreeEEG32 prealpha2 https://hackaday.io/project/165748-freeeeg32-prealpha2
And will be made FreeEEG32 alpha2 https://github.com/neuroidss/FreeEEG32-alpha2/tree/master/KiCad/out/3d with all bug fixes that was found in alpha1 test.