Skimming https://en.wikipedia.org/wiki/Wind_power_in_Germany it sounds like there is just a perpetual lag, where offshore wind is built and then it takes awhile to get it hooked in. It's been going on since at least 2014, and since that time like 5GW of offshore wind looks to have been hooked up, so I'm not sure there's a problem beyond "things take a while to build".