The FPGA 100MHz clock fpga_clk_100 on PIN_AW10 is incorrectly defined as a LVDS clock in the Intel® Stratix® 10 SoC Golden Hardware Reference Design (GHRD) version 18.1 and earlier. This can cause unexpected behaviour in the design for logic clocked from this source.
To resolve this issue, edit the IO assignment for fpga_clk_100 from LVDS to 1.8V (PIN_AW10) using the Assignment->Assignment Editor or Assignments->Pin Planner tools.
Note: If the design has been compiled the IO standard on the auto created LVDS complement signal fpga_clk_100(n) must be set to 1.8V. The auto created LVDS complement signal will then be removed automatically.
This fix is scheduled to be included in a future version of the Intel Stratix 10 SoC GHRD.