Problem compressing pure white

Hi, the plug-in is great and your compressing algo is the best one out there, i benchmarked every compressing tool i could find and the best Quality/Size ratio was from tiny. There is only one big problem, when compressing a photo with pure white on it RGB(255,255,255) some horizontal grey stripes start to show with RGB(254,254,254) on the smaller thumbnails that are visible with the naked eye (we have WooCommrece set up on the site with several thumbnail sizes). This makes for very bad looking product photos. If i resize the image myself and then compress it using the website (https://tinypng.com/) the image turns out fine. Could you please help, thanks.