Many of us are more than aware carved/lit Zilloween pumpkins turn into peptias/pumpkin pie at the end of the season. Many of us stored carved/lit pumpkins in SDB's for decorative purposes.
Several of us discovered interacting with the SDB after the season ended resulted in the pumpkins 'turning' inside the SDB.
Apparently carved and lit Zilloween pumpkins are attached to the specific holiday.
You can add new carvings on top of old carving, but the box count will only display the new.
Any attempt to interact with the 'old' carvings will continue to result in the items turning - Zilloween season or not.
Your Zilloween carvings are linked to the specific season in which they were carved, per a bug report to TS.
You've been warned.
ETA: Don't try to redecorate or move SDB's containing old carvings... they also turn about half the time.