Hi Chris,

I had the same problem several month ago on my Aquaris 4.5, I asked BQ for this problem.
They advise me to reinstall completly the last system image at this time, not only applying the last OTA, it solved the problem for me.
Today my phone runs with the UBports image with a working GPS.

Good luck...

Just select all your contacts, than share it with file browser, (must be installed first), it will be saved in contacts.vcf, send the file to your mailbox. To restore, copy the file on your new device, open file browser and select the .vcf file and share whith contacts app. I did this way when I moved to Ubports.