Pokémon Sleep has resolved several in-game issues through Version 3.6.3 and a recent server update while confirming that another display bug is still under investigation. The latest fixes correct a display error affecting the remaining days shown on the Relaxing Nap Ticket screen and an issue that prevented the “Pokémon Leveled Up” achievement from working properly under certain conditions. The development team also acknowledged an ongoing display issue affecting the remaining days shown in the Missions menu and Sleep Duration screen, noting that the bug does not impact gameplay progression and is scheduled to be addressed in a future update.
Source: Official Pokémon Sleep news
Nintendo & Pokémon Blog 