ESP32 as host: flash fails when WIFI enabled (ESF-8)

[thedayu]

Using esp32-wroom32 as host, trying to flash another esp32.

The example works fine but when I add code to enable wifi, flashing has very big chance to fails with error 2.
Packet could not be written! Error 2
in my case, i have a 1.5m bin file to flash.
WIFI disabled, always success.
WIFI enabled and connected, always fails at average progress 5%, max 16%.
WIFI enabled and connected, flashing task pined to core2, fails, average progress 26%, max 89%.

My guess is, some high priority task (WIFI) has compromised timing of serial communication.
But WIFI is mandatory in my case, any suggestion?