After the update that enabled the adjustment of HUD elements and custom sights in sniper mode, some vehicles have had their sights reset to default and the custom sight needs to be re-selected every time the vehicle is spawned.
This keeps happening even after saving the custom sight for that vehicle and saving a preset using the custom sight.
Vehicles I’ve observed this issue on are Leopard 2A4, Gepard(s), Tunguska, T90M, T90A and the Pantsir, but there are probably more vehicles having the same issue and I don’t know if it’s an issue with specific vehicles, or something else.