Wrong ims.apk path, crash com.android.phone after installing

[dkmgfk]

Build it by myself from the stock stable pie firmware. However the ims.apk is located in /system/priv-app. After changing that, the build script worked.

Here's the result.
ims.zip
build log
xubuntu 18.04 openjdk 8

However, imediately after installing the said apk, the signal lost, both SIM slots are showing as empty.
After a reboot, com.android.phone keeps stopping, signal lost again after a minute.
Signal restored after uninstalling ims.apk.
adb logcat
So this ims.apk is incompatible with treble aosp image?
Steps I've taken to build ims.apk:

1. Fresh installation of latest xubuntu LTS. 2. Install openjdk-8-jdk, simg2img and their dependencies.
2. Convert system.IMG, vendor.IMG to ext4 format.
3. Mount them.
4. Change /system/app/ims to /system/priv-app/ims in build.sh
5. Make the script executable.
6. Run the script.

Originally posted by @dkmgfk in phhusson/treble_experimentations#398 (comment)
Originally posted by @dkmgfk in phhusson/treble_experimentations#398 (comment)

[dkmgfk]

Also there's an mysterious "imssettings" app in stock ROM, under /system/app, don't know what it is for; some flashable VoLTE fixes for treble gsi image included this in zip.