[FS#52] TL-WR940N v3 and TL-WR841N v11: eth0 can't receive packets anymore after a while - Task opened (Attachment added)

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Florian Beier (Handle) 

Attached to Project - LEDE Project
Summary - TL-WR940N v3 and TL-WR841N v11: eth0 can't receive packets anymore after a while
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - After a while the receiving side of eth0 (WAN) seems to break. I ran tcpdump on my main router (ASUS RT-AC68U) and saw that the LEDE router still sends out ARP requests which are answered by my main router but don't seem to reach the LEDE router. After running "ifoncifg eth0 down" and then "ifconfig eth0 up" or pulling the network cable and plugging it back in everything is back to normal.
I already switched the LAN-ports of my main router, got a new WR940N and WR841N and changed the ethernet cables but the bug still occurs. The same bug is present in OpenWRT 15.05.

I attached a logread and dmesg-output but I didn't see anything special in them.

One or more files have been attached.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=52