I've mostly seen this in Lapis Lazuli, but it's happened to other Ores too. Despite being surrounded by Deepslate, the Ore generates in it's Stone variant still. It happens around Tuff too, but I'm not sure if that's intentional (makes sense if it does). Either way I hope this bug is noticed since it looks really good when it generates properly but fairly bad when it's not since it does not fit in (obviously). If this has been mentioned before I haven't seen it, sorry in advance if this is a repeat. Excited for future updates and bug fixes!