2.5.3. Handling Potential Jitter in Intel® Arria® 10 Devices
The RX path in the 50GbE core includes cascaded PLLs. Therefore, the IP core clocks might experience additional jitter in Intel® Arria® 10 devices.
Refer to the KDB Answer How do I compensate for the jitter of PLL cascading or non-dedicated clock path for Arria 10 PLL reference clock? for a workaround you should apply to the IP core, in your design.