Installation of ROM from 26/09/19 failed on XA2


I tried to update my device (OTA) my Sony XA2 from the ROM of 19/09/2019 to the latest one (26/09/2019), but the process somehow failed. The download was successful, but something went wrong during the installation: the phone has not rebooted (the /e/ logo with the bouncing dot appears, but nothing more…).
Is there a way to go back to the previous installation (just to avoid losing my system set up) or shall I reinstall everything from scratch (:"( in such a case, I guess I shall relaunch TRWP with a download image, right?)?

Thank you in advance

For information, I flashed the device again with Emma and re-installed, see