It turned out that both drives were dropped by a child. Their internal SATA contacts were slightly detached. It was not hard to disassemble the drives – you need to either lift the edge of the lid (WD) or unscrew and move the lid (3Q). Inside – hard drive and USB-SATA adapter. 3Q contained Hitachi disk :)
So I have simply disconnected the SATA connector and reconnected it back and it worked.
And another problem you could face — improper/broken USB cable connecting computer with external hard drive. Simply replace it with a good one.