Looks like I found a clue, if not solved the problem: in a code part of the savegame
<interests
lastIncreaseDelay="17" lastMissionSpawnedDelay="5" overall="1091">...
I have changed value "1091" to "500" (from the assumption, that it`s too large)
<interests
lastIncreaseDelay="17" lastMissionSpawnedDelay="5" overall="500">...
And then, to my great relief, new targets began to appear.
Hope, this information could be useful. Do not get stuck!)