I've not had too much in the way of technical issues since getting my PS5 at launch. There have been a couple game crashes randomly but two or three per year is what I was seeing with my launch PS4 as well so... not sure that's anything of note.
The only issue I've had really is my 4TB external HDD that I also had attached to my PS4... had an issue crop up over the summer that I hadn't seen before. My PS5 was able to see installed PS4 games on it but not launch them. It could play some of them like the Mass Effect Legendary Edition. In fact, that specific file hasn't had a problem yet. The quick fix was to delete and reinstall each game as the issue came up. I don't know if it's an issue with the PS5 or the external drive. Either way, once the game is reinstalled, there's no issue from then on.
For clarification sake, I've not seen any issues with the internal SSD on the PS5 beyond the abysmally small size.
As I've played Horizon and Ghost of Tsushima on my PS5, I'll point out that both are the physical PS4 editions. Not sure if that's different than what the OP has but it seems at least his copy of Ghost is a digital download. Wondering if digital vs physical have different issues on the PS5?