Only get data one time when i rebuild Poller Cache

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Hi i'm using a CentOs in a Virtualbox VM to monitor a Tomcat Server located in my Windows, but at the same computer, i'm monitoring some MBeans through JMX using some shell scripts. Executing these scripts the give me the data i want to retrieve, Cacti at some point is able to recover this data, but only after i rebuild it's poller cache manually, after that, when 2 cycles have passed i get no data again...
Any idea why this could happen?
In the image attached, you can see the poller executing the HeapMemory.sh script in 2 consecutive cycles, in the lower one retrieving the 4 fields asked, and on the upper one getting nothing...
Thks

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Data can be retrieved when the poller is executed manually from the shell. So my first guess was that it could be a permission issue, but i granted all the permissions to the script file... I even tried to execute the shell from a different location with the shell and everything worked fine, but cacti is still getting nothing two cycles after executing the poller manually.

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I made the script copy the output to a text file and when the poller is executed manually the result file is correct and filled with data, when the poller executes the script automatically no data is written on the file, just the headers. Any idea on where the problem could be? It seems like a permissions issue, but the script and all i thought about has all the permissions...