iMac 27", stains inside the screen

I purchased 2017 27" imac two years ago, and water stains has appeared under the screen right after 1 year warranty. Thing is I already replaced the screen once. Well... it costs about $600 in the Apple service store. Now the issue came back. Since the new screens comes with 90 days warranty, I can ask for replacing it again,, but I just want a permanent solution. I feel the quality of Apple products is getting worse...

Has anyone found any better way to resolve this problem?