In regards to the memory training: have you double-checked how much Ram your CPU actually supports, at what frequencies?
For example even the 7950X3D supports only DDR5-3600 when you put more than 2 bars of ram in, leading to issues with memory training taking long/not posting/instability if you enable any form of overclocking in that scenario.
I had that problem before and switching from 4 bars to two fixed everything.
Just in case this might be your issue as well.
In regards to the memory training: have you double-checked how much Ram your CPU actually supports, at what frequencies? For example even the 7950X3D supports only DDR5-3600 when you put more than 2 bars of ram in, leading to issues with memory training taking long/not posting/instability if you enable any form of overclocking in that scenario. I had that problem before and switching from 4 bars to two fixed everything. Just in case this might be your issue as well.