Affected environment - Iris bugfest.
Events of the type FEE_FINE_BALANCE_CHANGED are published by mod-feesfines but not received by mod-patron-blocks.
Publisher's logs (mod-feesfine):
PubSub knows that mod-patron-blocks is a subscriber:
But mod-patron-block doesn't receive this message. In PubSub history it's marked as "PUBLISHED":