CMTS is eventually restarted BSR2000

I have several BSR2000 CMTS, which eventually restarted, if one or more of its ports in return gets no signal.

For example when I have a single node fails, either because of lack of energy or by any court of fiber. After some time without reply in the port (U0, U1, U2 or U3), the CMTS restarts it.

Does anyone know if this behavior is part of its setting, or a problem of firmware?

The 4 that I have do the same, even one that was a BSR1000 also behaves the same way.

Thanks in advance

DrakerDG