This issue doesn’t show up on my Samsung Galaxy A5 (2016) SM-A510F “a5xelte”
For the SM-A510F were officially only provided by Samsung: StockROM Android 5.1.1, 6.0.1 and 7.0.0. An official Oreo 8.0.0 is not available - in any country, from any carrier.
I recommend an absolutely clean installation, which means …
After TWRP booted …
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click on “Wipe”
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Click on “Format Data”
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Type “yes” and confirm format action
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Once format data is done click on the “Back” button
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Now click in TWRP on “Advanced Wipe”
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Select Partitions to Wipe and check the checkbox:
✓ Dalvic / ART Cache
✓ System
✓ Cache
✓ data
✓ Internal Storage -
Swipe to confirm wipe action
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Once wipe is done, click on the back button to go back to TWRPs main screen. Click on the “Reboot” button.
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Click on “Recovery”, after that “Swipe to Reboot”.
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Wait until your device rebooted into TWRP Recovery, now you can flash the awesome /e/ OS ROM dev 9-pie.
PS. I have read your three postings here and here and here and am somewhat surprised by your observations and assessments.