I’m assuming that all of the network issues are the previously reported netdev watchdog timer issue. What is interesting is that the reports I found related to this were from quite some time ago on x86 machines. In one such case the distribution that the bug was reported for simply closed the bug as no longer supported because it was so old. Sometime after this issue appeared, the error seems to have simply gone away.
Since I never saw a specific fix to the related driver, I can’t say as to whether this was part of the infrastructure surrounding RTL8169 or the driver itself, nor can I say which kernel version fixed this. It seems fairly obvious the long term stable 3.14.x kernels don’t have the issue, nor did the R19.3 L4T kernel. Packages surrounding user space are unlikely the cause, as L4T uses the more modern surrounding packages both in R19.x and R21.x. What would really help is to know the first kernel version where the problem went away…other than knowing a specific kernel version to target, I’m not sure of a good way to fix this other than going to a 3.14.x kernel (very labor intensive and not easy).