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With a phone of 1 GB internal memory, I am able to install apps for 700 MB only. More than that I get the insufficient memory alert.
Total space 0.98 Available 71.49 Apps 601 Cache 1.88
Another phone of the same model is able to able to install apps for the entire 1GB.
Phone runs on Android version 4.2.x. Default write disk is external SD card.
Thanks in advance. Screenshots below: