Stm32h7xx is very different from stm32f4 and stm32l, in that it uses many more caches and other performance-enhancing techniques. Unless you add things like __dsb() and cache-related code where necessary (I explicitly disable cacheing in memory-regions where I use DMA, but ST seem to favour explicit flushing/invalidating before/after DMA) you are likely to hit problems.
This is a bit of a long-shot. What revision is your stm32h743?
Years ago I started a project around a stm32h743 (actually trying to port from a board that took stm32f767 because I wanted more RAM). But I have up after struggling for a long time with the SD-card interface. This was with stm32h743 Revision Y, which has loads of errata to do with its sdmmc peripheral.
I have recently revisited the project using the newer Revision V that has many of the sdmmc errata fixed. The sdmmc bit currently works (based on HAL; I am not a fan of HAL and I intend to rewrite the code when I get the opportunity).
