Unfortunately, increasing the buffer has not improved the situation.
journal.log:
Jul 03 15:51:20 colibri-vf kernel: ------------[ cut here ]------------
Jul 03 15:51:20 colibri-vf kernel: WARNING: CPU: 0 PID: 4 at /home/dev/ifm2_project/custom_data/build/tmp-glibc/work-shared/colibri-vf/kernel-source/net/sched/sch_generic.c:306 dev_watchdog+0x268/0x274()
Jul 03 15:51:20 colibri-vf kernel: NETDEV WATCHDOG: eth0 (fec): transmit queue 0 timed out
Jul 03 15:51:20 colibri-vf kernel: Modules linked in: virtio_rpmsg_bus usb_f_rndis u_ether vf610_rpmsg virtio virtio_ring libcomposite configfs
Jul 03 15:51:20 colibri-vf kernel: CPU: 0 PID: 4 Comm: ktimersoftd/0 Not tainted 4.4.220-rt197-2.8.8+ga54df82 #2
Jul 03 15:51:20 colibri-vf kernel: Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
Jul 03 15:51:20 colibri-vf kernel: Backtrace:
Jul 03 15:51:20 colibri-vf kernel: [<800133e8>] (dump_backtrace) from [<80013600>] (show_stack+0x18/0x1c)
Jul 03 15:51:20 colibri-vf kernel: r7:80534fbc r6:00000132 r5:00000009 r4:00000000
Jul 03 15:51:20 colibri-vf kernel: [<800135e8>] (show_stack) from [<802db2d0>] (dump_stack+0x24/0x28)
Jul 03 15:51:20 colibri-vf kernel: [<802db2ac>] (dump_stack) from [<80022a00>] (warn_slowpath_common+0x88/0xb4)
Jul 03 15:51:20 colibri-vf kernel: [<80022978>] (warn_slowpath_common) from [<80022a64>] (warn_slowpath_fmt+0x38/0x40)
Jul 03 15:51:20 colibri-vf kernel: r8:808e5380 r7:808b73c0 r6:8e7417b0 r5:8e5f1800 r4:80826e2c
Jul 03 15:51:20 colibri-vf kernel: [<80022a30>] (warn_slowpath_fmt) from [<80534fbc>] (dev_watchdog+0x268/0x274)
Jul 03 15:51:20 colibri-vf kernel: r3:8e5f1800 r2:80826e2c
Jul 03 15:51:20 colibri-vf kernel: r4:00000000
Jul 03 15:51:20 colibri-vf kernel: [<80534d54>] (dev_watchdog) from [<80065438>] (call_timer_fn.constprop.7+0x30/0xa0)
Jul 03 15:51:20 colibri-vf kernel: r10:8e5f1800 r9:80534d54 r8:808b73c0 r7:80534d54 r6:00000000 r5:00000000
Jul 03 15:51:20 colibri-vf kernel: r4:ffffe000
Jul 03 15:51:20 colibri-vf kernel: [<80065408>] (call_timer_fn.constprop.7) from [<80065644>] (run_timer_softirq+0x140/0x210)
Jul 03 15:51:20 colibri-vf kernel: r7:00000000 r6:808b7400 r5:00000000 r4:808b7400
Jul 03 15:51:20 colibri-vf kernel: [<80065504>] (run_timer_softirq) from [<80025a9c>] (do_current_softirqs+0x1ac/0x26c)
Jul 03 15:51:20 colibri-vf kernel: r10:00000000 r9:00000001 r8:04208140 r7:00000020 r6:ffffe000 r5:808b4250
Jul 03 15:51:20 colibri-vf kernel: r4:00000004
Jul 03 15:51:20 colibri-vf kernel: [<800258f0>] (do_current_softirqs) from [<80025db8>] (run_ksoftirqd+0x34/0x64)
Jul 03 15:51:20 colibri-vf kernel: r10:00000000 r9:00000000 r8:00000000 r7:00000001 r6:808b421c r5:ffffe000
Jul 03 15:51:20 colibri-vf kernel: r4:ffffe000
Jul 03 15:51:20 colibri-vf kernel: [<80025d84>] (run_ksoftirqd) from [<80041750>] (smpboot_thread_fn+0x2b4/0x2b8)
Jul 03 15:51:20 colibri-vf kernel: r5:ffffe000 r4:8e418ac0
Jul 03 15:51:20 colibri-vf kernel: [<8004149c>] (smpboot_thread_fn) from [<8003e1c8>] (kthread+0x108/0x110)
Jul 03 15:51:20 colibri-vf kernel: r9:00000000 r8:8004149c r7:8e418ac0 r6:8e462000 r5:8e418b40 r4:00000000
Jul 03 15:51:20 colibri-vf kernel: [<8003e0c0>] (kthread) from [<8000fb18>] (ret_from_fork+0x14/0x3c)
Jul 03 15:51:20 colibri-vf kernel: r8:00000000 r7:00000000 r6:00000000 r5:8003e0c0 r4:8e418b40
Jul 03 15:51:20 colibri-vf kernel: ---[ end trace 0000000000000002 ]---
Jul 03 15:51:20 colibri-vf kernel: fec 400d1000.ethernet eth0: TX ring dump
Jul 03 15:51:20 colibri-vf kernel: Nr SC addr len SKB
Jul 03 15:51:20 colibri-vf kernel: 0 0x9c00 0x8e7bb800 42 87416f00