New socket and new DDR standard teething, mostly, probably. Granted Intel seems to be doing a much better job with DDR5, so there's no excuse really for AMD.

For best results on AM5 prefer two-DIMM (1DPC) configurations, DDR5-6000 kits with EXPO, and avoid the Samsung B-die stuff (e.g. G.SKILL FlareX 36-36-36). If that's too complicated or whatever I would suggest waiting for Ryzen 9000 and the next wave of AM5 boards where this should all be ironed out, or go with Intel LGA1700 this generation.

Personally I am waiting for 64GB DDR5 UDIMMs and stable four-DIMM (2DPC) configurations before I can even contemplate upgrading from AM4. And since I'm already waiting I also want to see a faster chipset link (B650/X670 are still just PCIe Gen4 x4) and TB5 on my next board.