Alright. I uninstalled whole game and re-installed it:
First WinSPMBT.exe (basic game install) and then v6.0 Consolidation Patch.
Tested with
v6.0 and there everything
works!
Bombers release all bombs and fly away.
Next installed also
v7.0 (2013) upgrade, tested and it
fails exactly same way as described earlier
I didn't touch anything. Just installed recently downloaded v7.0. Settings were same in both v6.0 and v7.0 (hex grid off, training off).
Otherwise game works without problems. Just this level bomber bug.