Similar to when I updated from 13 to 14, the phone would stuck-app reboot loop (never showed the actual home screen but you could get to settings, eventually it would reboot on its own after several minutes) when my internally formatted sdcard was loaded. After giving it a dozen or so attempts, eventually wiped the sdcard by physically removing it, booting phone, forgetting the sdcard, shutting down, reinserting sdcard, and booting up the phone again which allowed me to reformat it as internal storage again.
As to how the phone itself works… not sure yet. It took all evening yesterday trying to get my sdcard apps to reinstall. 
Will try to report back later with any specific notes. Planning on seeing if I can easily Magisk it again like Android 13 or if that still bootloops like it did with Android 14.
Probably worth saying that the Play Store did see the phone as certified and limited store apps (Another Eden, in my case) were showing as available again.
I´m done the update right now. Takes app. 3 mins from end of download to second restart. That takes app. 2 mins - than I get the rotating leafes and it takes 2 mins for the reboot to finish. Since that time Android 15 works for me like a charm, but I didnt checkt all functions until now. Phone, threema, paypal, SD-card works. And I was very happy to see the charging limit also working! 
So I have to sayn a big THANKS to the team at the moment! 
Maybe buying a new SD card would be an option for you. You’ve had problems with it with recent updates, haven’t you? Mine hasn’t caused any problems yet, but I haven’t installed any photos or apps on it either…
I mean, it works as long as I format it again, and it wasn’t needed for 10 → 11 or 11 → 13, just in and out of 14. It kept working through all of 14, but… eh, whatever. Unlikely to replace it unless there’s something that clearly marks it as nonfunctional - reboot churn on major OS version upgrades feels like something failed there as opposed to the sdcard failing, especially when it works for months as long as there’s no major upgrade.
We have something special cooking internally, cannot wait to share it 
(You wouldn’t guess whats coming to your T2E!)
I am very hesitant to update to 15 after the recent 14 update has really made my phone a pain to use. It gets stuck constantly, closing and reopening apps, rebooting itself for no reason, and it’s all worse while charging. I feel like I really can’t depend on my phone in an emergency and it was stressful to travel internationally with recently. I’m also hesitant to update if the AI bot thing (don’t love that btw) is saying yet another new thing is coming. @Saijin_Naib @Sharad Please advise.
What AI Bot thing?
As for your device, I would recommend taking a backup of your data, upgrading to Android 15, and then doing a full device reset under Android 15 and re-setting it up.
Can I upgrade from 13.1.1 directly to 15.x or do I need to install the OTA offered 14.x first?
And is it just recommended to do a full reset on either of these upgrades or obligatory like it was going up to 13.x?
Also I think the AI Bot reference was referring to the intriguing post about what was coming to our Teracubes by the user @Terabot .
Stepwise major version (A13->A14->A15) is recommended to ensure migrations of userdata proceed as expected. If you can, please go stepwise.
Not unless you experience any abnormal behavior or issues not present under the prior version.
Ah yes, haha. Thank you!
Is the Terabot commenting in this thread not an AI answer bot?
Unfortunately backing up and resetting in that way is a little over my pay grade. The last time I backed up and upgraded (to 12 I think) it caused a lot of heartache and lost some stuff so I won’t be taking that risk just for a slower phone again, and will be looking for a new phone soon. It seems the software has outpaced the hardware at this point, as my phone gets worse with every update. My phone has left me high and dry too many times and is a daily inconvenience.
It shouldn’t be slower, and for nearly everyone, each major version is faster, as Android gets more optimized each release.
Typically, I see 10% performance increase in aggregate major version over major version.
In cases where the device misbehaves, a reflash is normally what is needed (and I’ve had to do this on my One/ruby, and my 2e/zirconia, for instance).
I can understand if you are at your frustration limit, however.
I would suggest you take the Android 15 OTA upgrade, at the least.
The android system updater for my Teracube 2e Zirconia now seems to be working as it should without having to download this update manually. I went through the process via the system updater of downloading and installing all the new updates sequentially from 13, and am now on 15.0.2. It took a while, but very happy with the results. The whole phone experience seems better. Great stuff! Well done Teracube. All I need now is a new battery and will be fully operational (but no UK stock).
Please use the Murena Shop for replacement parts outside of the US from now on:
I bought a spare battery and it was worse than the one that can with my T2e, whats with that?
I am sorry to hear that.
Where did you purchase the battery, and how is it worse?
Hi Sijin,
To clarify, I had my 2e for a year or so and the battery was not lasting more than a couple of days so I thought I would buy another battery thinking things would improve. Well, the new battery was not any better and now they both wont even get me through the day.
I have been done every thing I know of to extend battery life.
ending programs
shutting off screen
no back ground processes (developers options)
battery saver in settings
Thanks for reaching out,
When you look in Settings under Battery, in Battery Manager, what do you see taking up the most battery life?
Something must be going on, as a new battery should perform better than one a year or so old, unless your usage pattern is incredibly screen/cell radio heavy.
Android 16 is now available for Teracube 2e (2020) & Teracube 2e (2021) Android 16.0.1 for Teracube 2e 1st Batch Zirconia (SN: 2020)