Weird Docker Networking Issue After Restarting Containers

I'm a casual Docker user with some experience, but I recently set up a new Docker instance on Proxmox and Ubuntu 24.04, and I'm facing a strange issue. After I reboot the machine, the Docker apps work fine for a few minutes—accessible through a web browser from another device. However, after that initial period, they become unavailable, and restarting the containers doesn't resolve the problem. I've even rebuilt the whole VM, but the issue persists. It's not an overloaded situation since I only have two VMs on this machine, and the underlying OS runs smoothly. I'd appreciate any help on diagnosing or fixing this issue!