@linusthewise
Yes, your right. Our devices behaviour is very different. But you said that you hav a dual-SIM device (F8132). My device is a single-SIM device (F8131). I would think installation procedure is the same on both devices...
With the UT installation on my device it was important to do following both things before starting the UT-installer:

In case of flashing issues please wipe system, data & cache partitions using TWRP. Flash the OEM binaries from: https://developer.sony.com/file/download/software-binaries-for-aosp-nougat-android-7-1-kernel-4-4-tone/ using fastboot flash oem SW_binaries_for_Xperia_AOSP_N_MR1_5.7_r1_v08_tone.img

I have no idea how to solve the issues as I'm not a developer. And I hope some Dora-UT-developer reads our posts and could help to get the phones working and solve these important issues.