Receive messages when DB not available


currently we are migrating from 7.1.2 to 8.2.2 and we are facing following problem:
We have 2 ISs. First IS is not connected to DB second one is connected to DB. First IS publishes 4 messages into queue (subscription trigger queue) second IS subscribes them and starts the process model (each published message represents 1 step in process model).

That was a little bit of background and now the problem…
When DB is down (second IS cannot connect to it), and first IS publishes 4 messages to queue, then only the first message is stored there, which means that when second IS connects to DB again, then only the first message is subscribed. Forgot to mention that this trigger has some retry interval (see subscriptionTrigger.jpg). This approach works on 7.1 version, so I think we just forgot to set something, but don’t know what.

Do you have some idea what could be wrong?
Thank you.
(Oh and there is also picture of the model after the DB was started again: onlyFirstStep.jpg)