The term "performance issues" refers to any problems or difficulties that may arise in achieving desired results, meeting expectations, or completing tasks efficiently. Full definition
Further, there have been a few performance issues with the device along with the lack of apps, which is believed to have led to less than expected sales of the device. (goodereader.com)
However, the update was briefly suspended last week, after several users complained of performance issues on the device after installing the latest software upgrade. (indianexpress.com)
Government conspiracy theories aside, it might very well be because of performance issues. (slashgear.com)