Alright, so strange thing, but none of the titles in your landed_titles file actually have any entries in the mod's history files. You sure that that bug is what was causing the sprite issue?
Pretty certain as the issue vanishes when the file is placed in the landed_title area and returns when I'm running HIP + SWMH without it.
The b_mastropiero appears in title history files but not in the common\landed_titles which is what apparently causes unit sprites to default for some or all cultures according to the Wiki. It also appears to be date sensitive as starts prior to 1192.1.1 are fine. After that the sprites glitch to default as that is when the title in the history files has no holder and is inactive. Being active with a holder even with no defining in the landed_titles seems to not cause a sprite problem.
The file is from a few years ago last time I noticed this so I think maybe only the above mentioned barony is in HIP. Haven't checked the rest. The Validator has identified 3 others as lacking definition in landed_titles.