I cant reach my last router with SNMP

HI, i have four routers Huawei NE40E-M2K-B , and a OLT EA5800, i already discovered 3 of them, and the OLT.

But my last router, have been a pain, i'm discovering exactly as the other ones, but once it start polling the device, it says error, and start dropping everything.

I already correct my SNMP configuration, the configuration in every router it's exactly the same, so there wouldnt be problem with that, i think it's a bug, cause in one case it work but then stops working and start dropping everything.