The backhaul (i.e Openserve, DFA, Liquid) is only Layer 2 which the FNO provides to the DC which is usually Teraco. There it gets handed off from the FNO pe switch to the ISP. The ISP is responsible for its own internal routing up until the traffic breaks out from their core. Then they are...
You can try increasing or decreasing your MTU size. Given that your ISP supports the MTU. FNO and ONT most likely always support higher MTU. Could help with the problem a little bit. Otherwise it is nothing new to getPL and latency when the line is saturated.
The high-site is a snowball site, the horns on the structure are most likely sectors for wireless clients and not backhaul links.
As per @eddief1 you are past the building/FNO side already. There is a lot of loss after on the Layer3, will attach a screenshot of your results. I see the ISP has a...