Internal Storage seems to have filled itself back up again after deleting some media? Malware?

[Android Central Question]

Hi everyone. I'm using a pretty old Android Phone, Motorola Moto G (XT 1039) with Android 5.1.

I got rid of some saved Whatsapp videos yesterday to free up space in my internal storage, so that I could update a bunch of apps in the google play store that hadn't been updated in a while. More specifically, I deleted some of those videos and moved a couple others onto my phone's SD card. Afterwards I checked my internal storage in the Settings App and saw that I had gone from some 400-500 MB free space to about 770 MB. I figured this would be enough space to start updating.

I didn't update the apps right away but planned to do it the next day instead (so today). I had also restarted my phone in the meantime. But then this morning, when I tried to update even just one single app (Facebook Messenger with just a 38 MB update), it told me that I needed to free up more space. I went to check my internal storage again and it told me there were now only about 370 MB free! So I guess the storage filled itself up again overnight somehow?

I tried restarting my phone several times and tried to delete some smaller amounts of Whatsapp pictures to free up more space to see if anything would change or if I could repeat the process. But it just kept behaving weirdly: for example, google play would suddenly tell me I needed even more free space to install that 38MB Messenger update (now some 110 MB instead of just 3 MB previously), but when I looked in my internal storage settings, I actually already had more free space (440 MB) than before. It didn't make much sense. As of writing this right now, it doesn't seems to not be changing anymore at least.

Are these anomalies a cause for concern? My main worry to be honest is that this is a malware issue. I'm usually fairly careful with my phone - I avoid fishy websites, don't download apps outside of google play and I have two virus scanners (McAfee and Malwarebytes) that I scanned my phone with just today and that are up to date. I've read that checking if my phone is rooted might be another step I could take to decrease the likelihood of malware. Is this a good idea? Are there any other recommended steps I can take to check for malware?

I also tried checking my data usage and battery usage to see if any apps had been behaving weirdly. The only thing I noticed was Whatsapp having used a bit of battery power, even though I'd hardly used it. Another weird thing I noticed about 3 days ago is that my phone went through a lenghty "Optimizing Apps" process when I turned it on once. It was plugged in with a charger at that time, and I read that this is some sort of bug that can sometimes occur. But maybe it messed up my apps somehow?

I'd appreciate any advice. Thanks a lot guys!

 

[methodman89]

Sounds like you are synching your data. Turn it off then delete.

 

[B. Diddy]

Welcome to Android Central! You don't have much free space left to begin with, and certain apps (like Chrome) can build up their app caches pretty quickly. You might have to clear your app caches constantly, or start uninstalling more apps.

The system needs a certain amount of free space -- typically around 300 MB, but it can vary with the device. So just because an app is listed as being about 38 MB, that doesn't mean the system will let it install. Remember also that the app size that's listed in the Play Store is the size of the installer file, not how much space the full app will take up once it's installed (similar to the difference between a Windows .exe file and the size of the program once it's fully installed).