Yes this is a known issue with the s8 or s8+ on Oreo. We are working on a fix. One of the initial attempts to fix this has been released as part of [https://play.google.com/store/apps/details?id=org.mozilla.firefox_beta Firefox beta] if you have some time trying that build of Firefox would be helpful. It will install alongside the release version of Firefox so you don't need to worry about messing up your current settings. Letting us know if Firefox beta is less crashy would be a great help.