I have been unable to repeat the bug with the latest update.
At the end of the 5th mission I get:
==== ShutdownGame ====
CL_CampaignActivateStageSets: i = 2, stage->first = 0, stage->num = 4, stage->name = intro
Activated: set->def->name = ultimate_terror.
CL_CampaignActivateStageSets: i = 3, stage->first = 0, stage->num = 4, stage->name = intro
Activated: set->def->name = stop.
Campaign 'slot3' saved.
and then I can continue the campaign and actually play some more maps (my 6th mission which completed fine was the bunker).
PS: has anyone ever played the "oritental" map in the intro stage? I've played all the others but the oriental one has never come up for me.