I also had the same issue, I bought an SSD - same issue!
I found that sometimes unloading lspdfr in ragehook instantly restores the textures, I also found that adding the following line into the lspdfr ini helped (didnt resolve it completely though) - Main.PreloadAllModels = false
again none f this has fully resolved the issue but seems to delay it happening.
For me this only happens in the city, out in county it never happens which I thought was weird.
I also found some cool 2k texture packs instead of 4k as thought that might be an issue.
I hope this helps and also hope that someone can find a a perma solution for us!