Undestr flag preventing decay damage
I performed quite a bit of testing before posting and I have confirmed this issue only occurs inside a zone and also confirmed that this issue always occurs, it is not intermittent.

For any/all zones which have the UNDESTR flag set to true - decay does not cause any damage. The appropriate amount of resources are consumed from the TC for upkeep but once these resources are gone (or if the structure had no TC at all) the building does not actually decay. Everything remains at 100% health.

I am using these zones to create several small pockets of raid safety on the island for specific buildings but I still need the players to have to deal with upkeep. Fortunately only one player has noticed but I'm sure I won't be able to keep this hidden for very long. Any help would be appreciated.
Anything? This seems like a significant issue. Could someone at least confirm this?
i am haveing lots of trouble in just the last week as well. i set undstr and no decay but my zones keep decaying. 
This makes sense because entities do not take damage, they are not destructible. And decay damage would be removed as well.
I believe it would make more sense for decay damage to still be applied in an Undestr zone. This way upkeep could still be used, but if someone didn't want decay damage to be an issue they could simply use Undestr along with Nodecay. Just allows for another option. But, that's just me. 
Hi,
i want to create a zone with undestructable bases  so players can't do griefing in this PVE area but I also want decay and despawn to work properly.
unfortunately this is not the case as it does not allow decay damage so there are two unintended consequence
1. spawned things like hot air balloons dont disappear
2. bases with no upkeep don't disappear

can you help add additional flag for this option? thank you 
hi - what happened was all "spawning" items tend to clump up in the area since things dont despawn ie. vehicles, boats, etc.
its same problem on my server :(
agree with this. would be great if implemented
Has anyone found a solution to this?
I need to set a zone to undestructible so players cannot destroy others bases, but i would like the bases to decay.

Actually, yes. 

Change the IF section found at line 413 (in the currenent version 3.0.16) 

from...

  if (!(entity is LootContainer) && !(entity is BaseHelicopter))
  {
      if (HasEntityFlag(entity, ZoneFlags.UnDestr))
      {
          if (hitinfo.InitiatorPlayer != null && CanBypass(hitinfo.InitiatorPlayer, ZoneFlags.UnDestr))
              return null;
          return true;
      }
  }
​

to...

  if (!(entity is LootContainer) && !(entity is BaseHelicopter))
  {
      if (HasEntityFlag(entity, ZoneFlags.UnDestr))
      {
          if (hitinfo.InitiatorPlayer != null && CanBypass(hitinfo.InitiatorPlayer, ZoneFlags.UnDestr))
              return null;

          // Changes to allow decay damage to damage UNDESTR
          if (hitinfo.damageTypes.GetMajorityDamageType() == DamageType.Decay)
              return null;

          return true;
      }
  }

Pretty straight forward and has been working for me for a few months. Let me know if it doesn't work for you or if you see anything wrong with it.

how the ever hell did you find this fix? I'll try to test this when i can. thanks!

Not a big plugin developer but I am a C# dev and I was able to go through enough code to figure it out. Plus, necessity is the  mother of invention... in other words if I didn't figure it out I was screwed. :)

TRUE MAN TRUE TRUE TRUE AGAIN THANKS!

NKrRLs8kTrFGRMg.png FoamyTheSquirrel

Not a big plugin developer but I am a C# dev and I was able to go through enough code to figure it out. Plus, necessity is the  mother of invention... in other words if I didn't figure it out I was screwed. :)

Thank You for sharing this knowledge.
This should be implemented into the plugin for sure.