point 2 in your comments
My guess regarding simultaneous WiFi access from multiple board could be WiFi channel frequency.
Most of the demo application provisioning code use channel 1 and once provision done normal wifi access there is no channel defined.
Like below in provision mode (Access point mode)
g_provision_info.channel = 1.
if possible some one can change this like below in client mode
g_provision_info.channel = (uint8_t)(rand() % MAX_NUM_WiFi_CHANNLES); //random channel
define MAX_NUM_WiFi_CHANNLES 9 or 11
Keeping each device random channels may free up some of the issue.
smartchef project code can be modified like above. But every one download from Renesas sites its worthwhile ask them to change.