@Zhmak How are your internet providers set up? What is your link backup setup for the device? Do you have the device plugged into a UPS or battery backup?

When did this issue begin? Were there any changes to the network prior to this issue starting? 

NeilR_M wrote

  @Zhmak How are your internet providers set up? What is your link backup setup for the device? Do you have the device plugged into a UPS or battery backup?

When did this issue begin? Were there any changes to the network prior to this issue starting? 

First provider is static IP (with IP some aliases)

Second is configured via DHCP

Third is PPPoE

Load balancing weights set up as 5:8:1. And VPN service which fail too is on first provided.

Link backup is disabled. Shouldn't load balancing keep users online? Judging by the balancing weights, users access the internet through a third provider. And I connect to the VPN through the first provider. It's doubtful they're disconnected at the same time. The provider's equipment is also powered by a UPS.

Gateway is connected to line interactive UPS. And there is no power outages during this problem.

There are no log entries about internet outages or port shutdowns.

I don't know what started this. It happens too rarely to be related to any changes.

I set up a periodic reboot of the gateway every morning. This significantly reduced the number of freezes. Before, they happened once a week or more often.

Оccasionally strange message appear on the gateway physical console:

free(): invalid pointer

  @Zhmak 

I have seen this exact scenario. 

Do you have bandwidth controls enforcing bandwidth limits on the WAN connections?  I have found if you have more than about 4 rules VLANs will start randomly losing internet traffic, which can be resolved by togglign the bandwidth rule off and on again.

Keeping my rule set below a total of 4 and this has not happenned.  I have reported this

  @GRL