FBitWriter overflowed, only with the Oculus subsystem

For one of our projects we need to execute some client operations on server (for replication) in a reliable way. We are trying to run the game on a not so powerful network (5 Mbit downlink/ 1 Mbit uplink); just some seconds after the client has joined the session, this always causes, on the client side, a connection closing with the following message:

LogNetSerialization:Error: FBitWriter overflowed! (WriteLen: -1, Remaining: 4014, Max: 4014)
LogNet:Warning: Closing connection. Can't send function 'ServerOperation' on PlayerController_0': Reliable buffer overflow. FieldCache->FieldNetIndex: 32 Max 103. Ch MaxPacket: 512.

I understand which is the problem. The buffer of reliable events is full, so it cannot guarantee some reliable operations to be executed reliably, so its fallback is closing connection.

I tried to reduce the actors' replication frequency, reduce the number of reliable replicated events, increase the replicated buffer's size. The problem is still there, after some seconds the connection is shutted down. Apparently this problem is not strictly related to Oculus, but I also tried with the Null and Steam subsystems and, with both of them, the connection is stable for hours...

May you help to investigate on which is the real problem and which are the possible solutions?