Hi Folks,
As you can read at My experience on Sony Xperia XA2 topic, updating /e/ on my XA2 ended in “missing sim card & bluetooth issues”. As a result I used an /e/ build of early march. So i digged in this issue and did some ducking 
I found out this Sony uses A/B updates. (see https://source.android.com/devices/tech/ota/ab).
I then discovered if I installed a new build on my B partition it didn’t find the sim card No matter if I sideloaded it or uses the updater. Also I mentioned some errors in mounting the /firmware partition in TRWP if I set the active partiton to B. So some firmware files seems missing. My little quess is that Sony don’t install firmware on the B partition but they are packaging this with every update or their updater copies it.
Then I stumbled upon this pages:
- https://github.com/LineageOS/android_device_sony_pioneer/issues/1
- https://forum.xda-developers.com/crossdevice-dev/sony/progress-newflasher-xperia-command-line-t3619426
I followed this steps to install new firmwarm on my B partition using XperiFirm tool (for downloading the firmware) and Newflasher (to flash the firmware). After rebooting into my B partition /e/ booted fine but still the sim card error. 
So further actions had to been taken.
As you can read in the github link someone suggested to dd some firmware from A to B. Some ducking provided the right commands: LineageOS dd commands
After reboot /e/ booted flawless from both A and B partition. So I upgraded OTA.
By now I have the latest build on my B partition and the older one on A.
Happy 
