What version and rom of your Pro 5 ? 32 or 64 ? China/int/ubuntu version ? If your pro 5 is chinese version, did you have been change ID to int version to install int. version.
I have 32Gb int. version of Pro 5. I bought this second hand phone with broken screen, and then I bought replacement screen, change myself and works. Nothing problem with headphone. Thanks for your sharing, please let me know your experience about this problem

changind the motherboard... will delete all the info...  all the things that I have in my phone??

I can confirm that I also have this issue. Headphone mode only until the device is cooled down, I switch it off, and once cold (a few minutes in the fridge) and booted up it is back in speaker mode, and it usually stays in speaker mode but as soon as I use headphones it reverts to headphone mode and stays like that until cooled down and rebooted. Occasionally it reverts to headphone mode on it's own without rebooting or plugging headphones in, but not often.
I have replaced the headphone jack and that does not help.
Meizu Pro 5 silver/black originally Chinese version converted to UB ports Ubuntu touch.

Edited by User5207475740 at 2019-08-29 18:04

That's really a terrible situation I experienced. Can you know how annoying it is? When I watch a video, listen to music or even play a voicemail, there is no sound and just shows my iPhone is stuck in headphone mode. I think the situation is similar no matter for iPhone or Android. We can check the headphone and its jack port. Sometimes, it may be caused by software issue.  Specifically which method to use, you can look here: https://www.joyoshare.com/iphone-repair/iphone-stuck-in-headphone-mode.html
Hope you can get out of it soon.