E-Tile random issue

Hi, We are using E-Tile on Agilex for our design. We use linux-socfpga 5.15.100-lts. We have a test which will boot the board, wait for 45s, then ping the board from PC, which has an Intel E810 card and connects to the board through fiber cable. If ping is successful, we will reboot the board and repeat the test. In the meanwhile, there is a PTP master running on PC, which keeps broadcasting PTP sync packets.

The ping will fail after hundreds of reboot cycles. Sometimes, it only takes about 200 reboot cycles, sometimes, it takes more than 1600 reboot cycles. When the failure happens, the E-Tile statistics registers show no packets received. Have you seen such an issue? What could be a possible cause?