Why do gre-tunnels fall off in mikrotik?

Question

Mikrotik

Some time after the setup, the gre-tunnels between mikrotik RB2011 fall off.
Both points have white addresses. the network for tunnels 10.10.10.80/30
after some time from the central office does not ping 10.10.10.82 (time out),
and from the additional office ping 10.10.10.81 does not pass with the packet rejected message.
White addresses on both sides are pinged.

Answer 1

is input GRE allowed in the filter?