[Android General] Letitride:
Caution - my attempted fix might, or might not, work for you or anyone else - proceed at your own risks. Over the years, I've soft bricked (but recovered successfully) a # of smartphone by flashing, rolling back & updating firmwares, partitions and patches. For those that aren't fluent enough in English, please read carefully & do it slowly, one step at a time.

First, try this first as someone else suggested - Go to Settings > Apps & notifications > Camera (Ver 1.1.60.030) > Clear Cache AND Clear Storage. Then, exit & reboot the A5 Pro. Repeat this again. Then, open the Camera App & see if it helped or now. Click to switch to "front camera" & back to check, also the "wide angle main camera" - it might take a second or two to open. *** Notice (on the earlier System firmware V1.2 - the Camera App was shown as Camcorder (Ver 1.1.60.30)

Download & install "CameraMX" from Google Play Store as an alternate, see if that help to open & run the camera hardware.

This is the link to the offical UMI tech pages for the A5Pro, the firmware that is being suggested to rollback to, is V1.2 - either the EU variant or the "other" one for everyone else. All the *.RAR files & links are there and the English instructions written are good enough, I won't repeat them here in details -

https://community.umidigi.com/forum.php?mod=viewthread&tid=18789&extra=page=1

But, key points - read the tutorial & be comfortable flashing, the SPFT tutorial guide.

On a Windows 10 (Win 7, works too) - install & confirm that (USB) Vcom drivers are properly installed and recognized the A5 Pro.

Download & unpack/extract the full V1.2 (20190705) rom, it's 1 GB+ sized - with the "MT6763_Android_scatter" text file for use with the tool.

Both the full rom & the SPFT need to be unpacked in *.RAR and *.ZIP formats. Uncheck "userdata" options before proceeding to flash ("download" in the tool.) - follow all the steps outlined. Take a deep breath, and go ahead - it should take only a few minutes, finished successfully & you will see a checkmark for done. Disconnect the usb cable, restart & reboot the phone - everything as setup before should be there, not "fully" factory reset, i.e. WiFi & Google account settings, etc. remained. Do not open the Camera/App yet. Go to Settings > Systems and under Wireless Update - check for & wait for the V1.3 OTA update patch to show up, download & install - reboot when finished. Now, you open the Camera/App to check - hopefully, it will respond to user input. Another suggestions, lower the camera/video resolutions once you get it working, somehow - theory: it is less demanding on the hardware/apps.

If you did NOT uncheck userdata, then the A5 Pro would be wiped 100% clean, a clean & full factory reset = hours of restoring, setting up & downloading your Apps again. But, do this as a last resort if the above steps failed to get the camera/app working at all.

Great point about the video feature/functions - as a backup smartphone for me, I don't plan to use Skype, FB Messenger, Duo or WhatsApp to do video calling with the A5 Pro, but this can be a serious problem for others, counting on it to work. BTW, most of them, I can get my front/secondary camera to open & work, without freezing - my problem is with the main/triple camera ... maybe, this is our problem with early production batches as it was probably among the reasons for delayed shipping.

Please post back & share your outcome and success, and errors - if any. If possible, upload screenshots as it can be helpful to others. Good luck !