Yeah, I have seen that, too.
If that is indeed the cause I will instead blame them for not fixing the installer for months now, when a probable fix is known.
(Supposedly, this fork of the installer incorporates the fix, but I somehow couldn’t get it to run … GitHub - gronkern/ubports-installer: A simple tool to install Ubuntu Touch on UBports devices).
And I still think that we wouldn’t have all this trouble if they would prioritize function over eye candy, which should be a no-brainer.
You just have to compare the manual install scripts for Fairphone (Open) OS with the sources for the UBports installer … it would be funny, if it wouldn’t be so sad.
The 0.1.21-beta?
An older version of the installer was able to reboot to recovery on my phone, too … but this didn’t help to finish installing.