Hi
In the initial check i suggest that you should try the below steps:
1. In the MULTIWAN section (under WAN) in GUI, for both wan1 and wan2 interfaces disable/uncheck "Network service detection" settings
- Here basically you are disabling the mwan3/multiwan keepalive checks (which uses ping traffic to be sent to the default-gateway by default)
2. Click on Apply, and then do a permanent save to startup config
3. Next reboot your RV345 once after doing a permanent save to startup-config
Now observe for some time whether you are having the same issues as earlier
regards