I am currently running multi-wan load balancing behind 2 modems from the same ISP. Those modems have their firewalls disabled but are doing NAT due to being PPOE and having the same gateway which was causing issues with routing. I am running on this hardware https://www.amazon.com/gp/product/B01H2QJTM4/ref=ppx_yo_dt_b_asin_title_o07_s01?ie=UTF8&psc=1
I get packet loss, seemingly random. Both to ISP gateway, google dns, etc. The modems report no packet loss at all when this happens. I am starting to suspect the firewall...
I have a pretty basic config. I do not have sticky sessions enabled due to overloading one line or the other. This has not caused any issues with anything working as far as games, sites, streaming, etc. I do not have any static routes, or firewall rules configured by me. I do have a traffic shaper running to prio gaming over everything else and used the wizard to create it.
When the packet loss happens it will start with 10-20% for a few minutes and then peg to 100%, then a few minutes later(or after an immediate reboot) will go back to 0.
I think I'd start by unplugging one of the WAN connections to see if I could narrow down which one it is. Did you replace patch cables?
@teamits I have done this multiple times. It goes away with a single line but it does not matter which one.