Linux Bridge connexion unstable

[camexin]

Hi,

I have a Proxmox server with 7 Linux Bridge configured.
- one bridge configured on WAN interface
- 5 bridges configured on a subnet each
- 1 bridge configured on a subnet with /30. This subnet contain only 1 VM Linux Debian as a bastion.
This last subnet is unstable and I don't understrand the cause.
Il have reinstalled Linux without success.

Could you help me ?

Thanks
François