PfSense - Proxmox (KVM) failing over time

[pfsense-on-proxmox]

Hi
I've been using PfSense for years on Proxmox (KVM) virtualization. Previous setup was some years old running on a Lenovo HW with updated PfSense on it.

• This setup had occasional problem with PfSense failing over months of time (Proxmox uptime was +700days, so few times during it)
  Due challenging debugging - I've decided to do a new install few months ago - new Proxmox and fresh install of PfSense - Dell HW

The problem is back. Connectivity fails in really weird way:

• Connectivity that is constant (like batch jobs happening every hour or so) VPN's and other similar activities work. (validated from logs outside of the environment)
• "New" connections aka. connections that worked last week (scripts etc. so pretty sure they work) don't work - it's like rules not in memory wont load.
• This is now the second time this happens - so much shorter time periods than with the previous environment.

My environment is quite complex with 2 PfSenses and +10 VLAN, 2network connections, static routing etc.. (but no additional packages or other "non-standard" configurations) - so the debugging is challenging - and now due limited connectivity, needs to be done over terminal connections etc.

--> Any recommendations how to proceed with the debugging (what info to collect & how) and/or even better, any help on the issue?

thanks!