Nat network, UDP port forwarding doesn't work stable - after few minutes closing connection

[Lipsky]

Hello everyone,
I set port forwarding rules and I'm running virtual machine, after that i'm trying connect with application launched at guest via UDP from different computer in the same local network.
Everything works fine for few minutes, after that connection is closing.
I tested connection via TCP and everything works stable.
Host Linux ubuntu 18.04 64 bit
Guest: Linux ubuntu 16.04 32 bit
I tried install different versions VirtualBox and it's not helping.

Edit:
I did the same at qemu and everything works fine.

I would like to use Vbox for my solution that's why i need fix for this problem.
Thanks,
Piotr

[socratis]

We'd need to see way more than a simple description; complete and detailed setup of your VMs, logs, TCP/IP and UDP captures. Then you'll stand a chance of receiving a descent answer...

[Lipsky]

In attachments you can see more details about my VM.

[Lipsky]

Forwarding rules

[socratis]

We need to see a complete VBox.log, from a complete VM run:

• Start the VM from cold-boot (not from a paused or saved state) / Observe problem / Shutdown the VM (force close it if you have to).
• With the VM completely shut down (not paused or saved), right-click on the VM in the VirtualBox Manager and select "Show Log".
• Save only the first "VBox.log", ZIP it and attach it to your response.

[Lipsky]

vbox.log in attachment

I used wireshark for analyzing packet traffic and I see that at some point (after few minutes) packets don't leave virtual machine.