Bug - two ships recovered at once after undocking

[Agarwel]

PS4 (no pro), career mode. Main mission to perform docking on or around Kerbin

1) I shot one rocket to the orbit

2) I shot second rocket to the orbit.

3) I docked them together (mission completed)

4) I undocked them and brought one of them back to the ground.

5) After recovering the vessel, both ships were recovered (including both pilots, etc). The second ship did not stayed on the orbit.