Chosen Solution
I just replaced my iPhone 8 Plus housing, since it was dropped and got bent and the back glass was also cracked. Now the SIM tray keeps getting stuck, I have to open the phone and manually press the eject button inside the phone. It looks like the small pin for ejecting the SIM tray keeps hitting the logic board. Background: I got the phone in bad condition (cracked back glass & bent housing), and I am trying to fix it. The seller lied to me by telling me that the phone has no history of repair, but when opening the phone there are a lot of missing screws and the adhesives are gone (for battery and display).
This was caused by the missing screws, so the logic board keeps getting misaligned inside the phone, which causes the small pin for ejecting the SIM tray to hit the logic board. My temporary solution was to wedge a paper between the logic board and the display. Now, I was able to put all of the screws, and the SIM tray does not get stuck anymore.