Repeating values in mean period of wind waves (MPWW) and mean direction wind waves (MDWW)

Hi all,

In the ERA5 hourly data on single levels from 1940-present, i downloaded a single year (2003) of mean period of wind waves and mean direction of wind waves for a specific region on the west coast of the UK. However when I plotted wave roses of the data they looked very odd and I checked the data on excel and there is definitely an odd amount of repeated values for MPWW. The main repeated value was 3.84906. Overall 70% of the MPWW data falls between 2-4 seconds, and an obscure amount of this (20%) falls into 22.5-45 degrees MDWW. Has anyone had similar issues? or does anyone know what could cause this issue?

Thank you!