The main bug left that I know about is Villages and Workshops destroying Flood Plains but that will will be quite an extensive fix, affecting numerous files. It would thus require a reinstall and is likely to be incompatible with current saved games (I'll have to check) - may be best to leave it until 1.19.
Disappearing Flood Plains are a serious issue. If they cannot be fixed until 1.19, then I would disallow Flood Plains Cottages and Workshops in 1.18. It's no fun playing against an AI with ruined desert cities. Flood Plains Farms and Quarries would still be available; maybe you could allow Plantations, too. Either way, I think the bug does require some immediate response.