I exclusively play on B42, with only my mods, and I have never seen any of these issues.
Please elaborate on what you mean by 'as a result of my attempts', and tell me which version of WZ you're using.

I have only 2 mods installed for the zombie modification, your mod and Definitive Zombies, but when I turned off Definitive Zombies, the issue still did not go away, there was no error message in the error box, I am using the current version of your mod, in the mod settings I only enabled Wandering Zombies without the (WIP) suffix, below I have attached a link to a video example of what it looks like, and I have attached a link to a photo that shows the problem itself. I also want to add that when the problematic zombie is under the map, it does absolutely nothing, and only starts to move or perform some actions when I get close to it.

https://youtu.be/B1QZDkPT14E
https://i.pinimg.com/736x/a3/d9/96/a3d99682bb5a35e27a231dc0ee750270.jpg

Post your full mod list.

when I use the simple version of Wandering Zombies, this problem appears much more frequently and in larger quantities, whereas when I run Wandering Zombies (WIP), this problem occurs much less often.
https://youtu.be/Ku6hXfSQev8

Disable Bandits, and let me know if it still happens.
Every time this comes up, Bandits is always involved, and so far that's always stopped the disappearing into ground issue.

Okay, I will try, thank you for the advice.

You were right, by turning off the bandits I no longer notice zombies underground, but with the solution to this problem, a question has arisen: will your mod support good performance together with the bandits in the future?

WZ WIP already has Bandits compatibility.
According to others that have experienced the issues you've described, if you run Bandits alone you'll occasionally see the issues in B42.

I haven't been able to confirm this myself. No matter the configuration I've used:

• Bandits alone.
  
• WZ WIP alone.
  
• Bandits + WZ WIP together.
  
• Bandits + Extra Options + WZ WIP together.

I have never once seen any of the issues, so I can't even begin to debug what's going on.

I have this problem even when I use WZ (WIP) with bandits.

As I said in the rest of my post, Bandits alone appears to cause the issues. There are even comments on the Bandits workshop page that suggest this may just be a Bandits issue in B42. I have not personally heard of any these issues happening in B41, either, whether you run Bandits alone, or with WZ (either version, for that matter).

And which version of the bandits are you using? And have you changed the zombie settings in the sandbox?

I don't use any version of Bandits, as said, I only play with my mods, and no other. For testing, I used what is now called v2. Once again, despite never seeing the issues myself, no matter what I do, there are numerous comments and discussions about Bandits causing these problems in B42.

Apart from population and respawn settings, I only change the sound follow distance. I use my own version of Random Zombies / Definitive Zombies for adding sprinters, smart zombies, etc.

I understood, you simply said that when you were testing with the bandits, you found nothing similar, and I became curious whether you were using a different version of the bandits, so I will solve the problem with them, thank you for your help.

The distinction needed to be made clear, between playing and testing. It's very well possible I would see the issues myself if I played with Bandits, that is, used Bandits for any considerable amount of time.

In testing, what I do is very limited to what the potential cause of the issues would be, so it is never an extended period of time. In this case, I know two causes of the zombies falling in the ground, and that's what I tried to reproduce:

• Broken animations.
  
• Messing with zombies that are sitting against walls.

Both of these 100% of the time lead to zombies falling into the ground. Bandits does make changes to animations if I remember correctly, which could be the cause of the issues. As for messing with zombies that are sitting against walls, my brief glance at the source code for Bandits didn't make it clear whether it was, or wasn't.

Essentially, I ended up doing the same you did in your video, ran around town/buildings so I could try and see if any sitting zombies fell through the ground: I never did. Unfortunately, outside Bandits, I have yet to see any other mod(s) that are being used by everyone that is experiencing these issues, suggesting it is Bandits itself.

Initially, it was assumed that Extra Options was causing the issues, as they seemed to go away when people stopped using it, however, not everyone used Extra Options. What gets me, is that WZ seems to compound what appears to be a Bandits issue, despite the compatibility, not touching animations, and not doing anything that would break zombies sitting against walls.

This is everything I know about the issues as it stands, and I personally suspect it's an animation related issue, as B42 has had changes to the animation system, along with the addition of ragdolls potentially being relevant here.

If you happen to discover anything that you believe would help figure out what's going on here, let me know.

The problem may be that the bandits v2 are using mod options build 41, while I am playing on build 42.But when loading mod options b42, the problem still did not disappear because the bandits need mod option b41.