ESP32-C3 occasionally does not respond to ARP request

[Phonog]

Hi all,
I have a system where two boards communicate by wifi. One of the board (board 1) uses a ESP32-C3 as a coprocessor that handles the wifi. The traffic is about 3 UDP frames exchanged per second both ways.
Each time the board facing the ESP32 (board 2) wants to send a UDP frame to the ESP32, an ARP request is sent, to which the ESP32 replies with its MAC address, then the board sends the UDP frame to the ESP32.
Every now and then (typically 1-3 hours), this fails. The board 2 sends the ARP request, but the ESP32 does not answer. After sending 8 requests (for a total duration of 1.5 s), the board 2 gives up and my system stops in an error state.
Why does the ESP32 fail to answer the ARP request? Is there some required initialisation or configuration that has been overlooked?
Thanks.