So, today I rooted my Samsung Galaxy S3 Mini. I used the instructions and tools listed on this site: (German text, use Google to translate) http://www.chip.de/news/Samsung-Galaxy-S3-Mini-Root-Anleitung-zum-Entsperren_61223279.html - TL;DR: I used Odin to Flash the system, whatever that means. I do not fully understand the process.
For about two hours everything was alright and I was happy. But then, out of the blue, the phone froze. It happens sometimes, so I didn't worry, but now it happens about a minute or so after every boot.
The phone reboots by itself if left alone after freezing. When on standby, the issue does not occur. Safe mode does not alter the behaviour. I also tried wiping the cache partition, per the option in the recovery menu.

What I have not done is trying to undo the root or a factory reset - both of those are last resort solutions to me that I would like to avoid for as long as possible.

Are you certain the custom recovery is at its latest version? If so, try running adb logcat to capture the state of the device right on boot. However, I'm suspecting this is a firmware issue being manifested here, so it will not appear in the logcat, in which case I would conclude that the ROM must be incompatible in some way.

I am pretty sure the ROM is compatible and up to date. The site from which I used the tutorial is pretty trustworthy (even if the ads are annoying) and the tutorial, written for my phone model and OS version, linked to a specific file. Again, what's weird, the issue wasn't there at first - the phone froze suddenly while I was normally using it, and now the same issue happens after every boot process.
And how do I run adb logcat? I downloaded an app which seems to display logcat entries in real time, but there was no indication of a problem before it crashed, even the log entries kept flowing up until it crashed, i.e. I am not sure about touch responsiveness, but the display itself didn't even freeze. I am not sure I did the correct thing, though.

In other news, it seems I can avoid the freeze and crash issue if I activate standby just after booting and wait for some time - I am not sure how long, though. It does freeze eventually, but I have more time to do whatever I need once I wake it up again.

If there is no other solution, I am willing to undo the root. In this case, do you have any recommendations for alternative root processes I can attempt? I don't mind custom ROMs and such fancy stuff, I'm really just looking for the root permissions.

Adb logcat is run on your PC while its hooked up to your device; adb is part of the android development toolchain.


Why root a device? Do you really need it rooted?

Ah, I will keep that in mind. Thanks.


No, not "need", but it has benefits. And I decided that, for me, the benefits are more than worth the risks.

Edit:
Update - I managed (or so I hope) to do a backup of all my essential stuff and did a factory reset. It didn't help. I am currently downloading the stock ROM and will attempt to undo the root shortly.

The point of Logcat is to investigate the cause of the issue. If the log appears to continue even after the system appears hung, this means that the UI thread is waiting on something, but it is not clear what, or there is a problem trying to receive inputs. If you are able to press the power button to turn the screen off, this may indicate that the root you downloaded is trying to modify the touch screen firmware.

I have now successfully removed the rooted ROM and installed the stock one. Aside from some minor glitches and data loss that are both acceptable my phone is back to normal. I shouldn't have done the factory reset - that's the only place in the whole story where things got deleted from my phone.

In case anyone could help resolve the glitches: It is an app that I cannot install, lichess to be exact. I had it installed prior to resetting the phone. Now I cannot install it again, it says that it is incompatible with my device. The browser version of Google play reports "No carrier", and I also noticed that my play store icon is the old one, not the one they put in a recent update. I went into my settings in the software update menu and tapped "Check for updates". I received a popup saying that my device was altered and no software updates are available. I tried reverting play store to the first version and updating it again, but there was no result, it keeps updating to some old version.
I figured the device detected that it had a custom ROM installed at some point and now doesn't install the last updates, and that's also probably causing the lichess incompatibility issue.

I can live with both of those glitches, it is not tragic, but it would of course be nice to solve them.

It appears that the stock ROM you installed comes with a very old version of GApps (Google Apps). If this is the case, use the Open GApps website to generate a zip file with the latest version of the apps; I believe Samsung uses either mini or full. Then, use your recovery to extract the zip file into the system directory (it "should" know what to do). Once this is successful, clear the cache again and restart.

Thanks a lot for the link you provided! Unfortunately, it seems that the site has nothing for Android 4.1.2 - if it does, what zip file should I chose?

Hmm... that version corresponds to CyanogenMod 10 - try gapps-jb-20121011-signed via Team Android. Be aware, however, that the apps are extremely old - I have this idea in my head that 2012 was the "golden age" of the Google ecosystem - but anyway, do carry on updating all of the apps, although I fear it may be too old at that moment in time to update to the latest and greatest.

Hence why I am looking for people to make a large compendium for Android tooling - it's horrible how fragmented the Android community has become. XDA Developers is no compendium - more like a giant crowd of confused people conversing to each other in not-so-great English... [/rant]

In the time that has passed, I have tried updating my gapps, but without any change - it seems to install the very same version over and over. What's even more curious, I tried to get the .apk package for the app directly, through a third party website that grabs them from the play store and lets me download and install the packages manually. And it failed to install, with an error that I don't remember exactly, but it was something about compatibility issues. This leads me to believe that my current OS is indeed, for some reason, incompatible with the app. How is this possible?