sounds like you have a pass-through device, which can only be used by one VM at a time, or the VMs are heavily over-provisioned, ie more memory combined than host can handle.
Is there anything interesting in "qm config 100" and "qm config 101" outputs?
Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox
here it is
100.conf
agent: 1
boot: order=scsi0
cores: 4
ide1: local:iso/virtio-win-0.1.229.iso,media=cdrom,size=522284K
machine: pc-i440fx-8.0
memory: 8092
meta: creation-qemu=8.0.2,ctime=1691682920
name: 100
net0: e1000=C6:BB:7A:33:24:24,bridge=vmbr0,firewall=1
ostype: win10
scsi0: local-lvm:vm-100-disk-0,size=64G
scsihw: virtio-scsi-pci
smbios1: uuid=eab3248c-d935-4044-8d55-9c0528bb7df8
sockets: 1
vmgenid: 6e6cf5b9-16cf-499f-b50b-e1bb26f5acd1
101.conf
agent: 1
boot: order=scsi0
cores: 4
ide1: local:iso/virtio-win-0.1.229.iso,media=cdrom,size=522284K
machine: pc-i440fx-8.0
memory: 8092
meta: creation-qemu=8.0.2,ctime=1691682920
net0: e1000=E6:32:78:FD:30:CE,bridge=vmbr0,firewall=1
ostype: win10
scsi0: local-lvm:vm-101-disk-0,size=64G
scsihw: virtio-scsi-pci
smbios1: uuid=65501cd7-a2ef-460d-bd6d-4f2fe78f8bb4
sockets: 1
vmgenid: 66ec19b5-d03c-4977-93b6-40b408647417