I'm not familiar with the mod, but looking it up; it does say it's deprecated:
https://www.nexusmods.com/stardewvalley/mods/8111?tab=files
You could try switching to that "Modular Gameplay Overhaul" mod that it recommends.
Though we may be able to glean some more info from a log:
https://smapi.io/log/
I managed to find your other post; thanks for posting a log. I am seeing 3 different mods editing SpecialOrders.
Code:
23:33:08 TRACE Ridgeside Village (SMAPI component) Registered RSVSpecialOrderBoard
23:33:08 TRACE Stardew Valley Expanded Applying Harmony patch "HarmonyPatch_UntimedSpecialOrders": postfixing SDV method "SpecialOrders.IsTimedQuest()".
23:35:25 TRACE SMAPI Content Patcher loaded asset 'Maps/zrsvspecialeffects' (for the 'Ridgeside Village (Content Patcher component)' content pack).
23:35:25 TRACE SMAPI Content Patcher loaded asset 'Maps/zrsvspecialeffects' (for the 'Ridgeside Village (Content Patcher component)' content pack).
23:37:37 TRACE SMAPI Content Patcher edited Data/SpecialOrders (for the 'Stardew Valley Expanded' content pack).
23:37:37 TRACE SMAPI Content Patcher edited Data/SpecialOrders (for the 'East Scarp NPCs' content pack).
23:37:37 TRACE SMAPI Content Patcher edited Data/SpecialOrders (for the 'Ridgeside Village (Content Patcher component)' content pack).
23:40:23 TRACE SMAPI Content Patcher edited Strings/SpecialOrderStrings (for the 'Stardew Valley Expanded' content pack).
23:40:23 TRACE SMAPI Content Patcher edited Strings/SpecialOrderStrings (for the 'East Scarp NPCs' content pack).
23:40:23 TRACE SMAPI Content Patcher edited Strings/SpecialOrderStrings (for the 'Ridgeside Village (Content Patcher component)' content pack).
23:50:08 ERROR game NullReferenceException: Object reference not set to an instance of an object.
at StardewValley.ShipObjective.OnItemShipped(Farmer farmer, Item item, Int32 shipped_price) in stardewvalley\Farmer\Farmer\SpecialOrder.cs:line 2077
at StardewValley.Game1._newDayAfterFade()+MoveNext() in stardewvalley\Farmer\Farmer\Game1.cs:line 9158
at StardewValley.Game1.<>c.<newDayAfterFade>b__716_2() in stardewvalley\Farmer\Farmer\Game1.cs:line 8714
at System.Threading.Tasks.Task.InnerInvoke()
at System.Threading.Tasks.Task.<>c.<.cctor>b__277_0(Object obj)
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
--- End of stack trace from previous location ---
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot, Thread threadPoolThread)
SDV Expanded itself mentions modifying the special orders to be untimed. Though, it could be a vanilla issue as well.
Do you know if the active quests are modded special orders or not?