Node Manager logs might repeatedly show a similar error as below.
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INTERNAL ERROR. Append is False but OutputFile [C:\appData\Programs\tibco\tsnm\<version>\nm\logs\MemoryStatisticsLog.123456-a111-222c-333c-dd123456.txt] already exists.
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"Append is False but OutputFile already exists" error in Node Manager logs.

This error might seen if the memory statistics log file located under node manager logs is stuck as a result of an improper/unexpected Node Manager restart.

To get rid of this error, delete or move the memory statistics log file displayed in the error message, from the location displayed in the error message.

Note: Check the instance id in the error and delete/move the same instance's memory statistics log file. The memory statistics log file name will be the same as shown in the error. For example, in case of the error mentioned in the description section above, the issue would be with the log file "MemoryStatisticsLog.123456-a111-222c-333c-dd123456.txt" located under "C:\appData\Programs\tibco\tsnm\<version>\nm\logs" and hence the same log file needs to be deleted.