Nighthawk M1 Mobiler WLAN Router / 4G LTE Router MR1100 - charging problems

Hi all,

I newly get the router and have very strange behavior. From beginning charging was absolutelly OK. But after I removed buttury and trried to use router without buttury, only via cable, it does not charge anymore and does not react on put or remove USB-C cable.

If router is connected to charger and I remove buttary and put them again, it is charged. But only in this case.

Another observation: router was warm first day of using. Now it is cold, always.

I did open a  ticket by support. But my questions is: is it a bug or feature? If feature, how to use it correctly?

Many thanks in advance, Leo