Windows 10 Professional (x64) Version 1903 (build 18362.267)
Graphics: Intel(R) HD Graphics 630
Here is an attached blend file that illustrates the issue (visible in render preview as you switch between eevee and cycles).
If you compare the outcome of mod(x, x) between eevee and cycles. Cycles seems to correctly evaluate that to 0 while eevee seems to evaluate that incorrectly to 1 for many values of x (for both integers and fractions).