Thin green bar propagation disappeared?

RotoBrush. The thin green bar that crawls across the frames sequentially is no longer present. So instead of caching the calculations so that it can propagate relatively, it propagates absolutely i.e. from the base frame everytime:

Propagating...

1 2

1 2 3

1 2 3 4

1 2 3 4 5

1 2 3 4 5 6

1 2 3 4 5 6 7

Absence of the thin green bar surely indicates that there is no cache?