Using SIM in different SIM tray not possible

Hi all,

I switched to iD mobile recently. Everything is going fine and I'm getting some good speed here in Leeds - but I did some further testing for fun (and because I also have a three payG SIM for trips to the US that I used for a comparison).

For some reason, I noticed that the signal strength icon on my Samsung S23 ultra (almost always) seems to show one bar less signal strength on my iD SIM than on my three SIM. Using apps like gmon-pro confirmed though that the signal strength should be identical and that I'm indeed connected to the same mast and band. Speedtest do not show any difference, either.

I wanted to test if that's maybe a Samsung issue and wanted to swap the SIM cards around so that they use each other's SIM trays.

I noticed that the iD SIM now absolutely doesn't want to activate in the SIM tray 2. I tested the SIM in different phones and different SIM cards in the tray... It seems to be an iD SIM + sim2 tray issue only?

The only thing I also noticed is that when I put my iD SIM in an older OnePlus phone, it gave me a chip like looking icon for the SIM (instead of the regular SIM logo like for other cards).

My question is therefore - is iD mobile using some special type of SIM? I read stuff about UICC SIM cards? Maybe iD installed some verification certificates on my Samsung phone that prevent me from using it in another SIM tray? I haven't tried resetting the network settings, yet - because I'm too lazy... But maybe that could help...

In any case, putting the iD SIM back into tray 1 and three back into tray 2 doesn't cause any issue...

Super weird behaviour from the SIM haha