Transaction with node's API not confirmed when server runs for some hours

Hi there,

I have been trying to figure out this issue for some time now.
I am running an NIS node on an Ubuntu server and am trying to send a transaction using the prepare-announce API call.
Everything is working great and the transaction is made and confirmed some seconds later.

After some hours that the node is running if I’m trying to send another transaction it seems like the transaction is sent but it’s not really being sent. I’m getting a transaction ID and in the log it says:
2018-03-16 16:44:01.060 INFO entering /transaction/prepare-announce [127.0.0.1]^[[0m (org.nem.nis.controller.interceptors.AuditInterceptor preHandle)
2018-03-16 16:44:01.064 INFO exiting /transaction/prepare-announce [127.0.0.1]^[[0m (org.nem.nis.controller.interceptors.AuditInterceptor afterCompletion)

But the transaction is not being confirmed after that. Only if I restart the NIS Node server it will work again.
What am I doing wrong?

The node is still working and still receiving new transactions from the blockchain and it seems from the logs that it’s still working flawlessly. The only problem is that I can’t get the transaction to go through.

I tried reading anywhere but I’m not finding any answers so if anyone could please help me that would be awesome.