My ISP can't force-update that model so I have to update it manually. But where to get the firmware and how to update the device?
The current firmware:
Bootloader Revision: 2.4.0beta3_R8
Current Software Revision: e3928A-E15-5-E122-c5110r55113-160318c
Firmware Name: e3928A-E15-5-E122-c5110r55113-160318c.bin
Firmware Build Time: Mar 18 09:53:37 2016