It is not the forum issue but it is a message from the OS of your mobile device, try to go to developer options, scroll all the way down, and uncheck or turn off the 'DO NOT KEEP ACTIVITIES' option. just turn it back up, if you want, when you're done with your upload.
"Most of the Android user`s experience the error "unable to complete previous operation due to low memory" even if they have a 4GB internal memory. If you are using the Official Google Chrome browser on your Android device and you always encountered this everytime you open Facebook for instance, I would advise that you download another browser like Firefox. You can download Firefox beta on Google play store. Also, if you are uploading a photo using Google Chrome and the error alerways appear, you can try the ES File Manager. You can easily access your files from your device and share them with others"