When a pen writes flawlessly in continuous text but, after a pause of only a few seconds, needs one or two strokes before the ink comes again, a fault is rarely the cause. With obliquely ground nibs such as OM, OB and especially OBB, the usual culprit is how the pen is held, because these grinds only lay down ink cleanly within a narrow range of angles. If you tilt or rotate the pen without noticing when you set it down again, the nib no longer meets the paper with the whole of the ground face, and the stroke comes out dry. A consciously consistent grip is the remedy here, and simply trying a different angle will soon show whether that is the problem.
The state of the nib slit and the ink also play their part. Inks differ markedly in how freely they flow, so switching to a wetter-running brand can help noticeably; merely swapping one document-proof ink for another writing ink, by contrast, often changes little. If the behaviour persists, the next step is the dealer: according to the service documentation of the period, the nib could be exchanged for a different width free of charge within the first six weeks after purchase (as of 2006), so an OBB nib that proved impractical could be replaced by a B or an M at no extra cost.