Telemetry interval Problem

So we had two routers positioned on high mountains around the city, all RAKS, one of them with a BME680 Module for environment telemetry.
Also some stationary and mobile Clients with BME680.
All ran on 3600s Interval and everything worked fine.
Now we extended our Mesh with a third Router+BME680 on a mountain about 10km away.
Pretty soon as we turned it on, the telemetry data (battery, environment, Neighbor Info) stopped broadcasting on every node in the Mesh.

I watched the ChUtil and it peaked to about 55% and then dropped to 20-30%.

now when I change the interval of one Node, this Node seems to work until I change the interval of another Node.

Am I missing something?
I know there is a safety feature that disables S&F, Range Test and GPS broadcast at higher ChUtil.