Curing Villagers doesn't keep the discount permanently

After doing some trades with my cartographer, the price with the glass pane has been reset, yet there is no mention of this happening in the patch note ( i think ) This happen to both carthographer i had. This was annoying to me the fact that i'd have to keep recuring villagers just to keep the price low on a useful trade. I doubt it because of my optimization mods since it doesn't change vanilla gameplay at all. (Edit, i tried in vanilla, the problem persist)
This is not a visual bug and oddly enought, after a day, it came back to normal only to be bugged again and back to normal.