Here is the second interesting thing I had happen to me with villagers and nether Portals:
So i don't have pictures (I uploaded them but something weird happened and now I can't access them) to show exact cords of the portals so I'll use examples
N=Nether
O=Overworld
1N is linked too 1o
2N is linked too 2o
1N cords= x:100 y:100 z:100
1O cords = x:800 y:100 z:800
2N cords = x:300 y:150 z:300
2O cords = x:2400 y:150 z:2400
(Again I know it's not exact cords but this example show kinda the same space as the portals in my world so it's not prefect but gets the point across)
I was transporting 2 villagers, (leads with boats) I went through 1O with both villagers and they both went through just fine, no hiccups, so I lead both the villagers at the same time too 2N and unattached one and pushed it through, out of the boat, went through the portal myself too 2O and the villager was there everything was fine, trapped the villager and kept it safe. Went back through the portal into the nether and the other villager was where I left it, so I destroyed the boat it was in and pushed it through 2N and went through. Here's where things get alittle funky, when the chunks were loaded, I expected to see 2 villagers at 2O, but there wasn't, there was 1, the second one wasn't there, so I was bummed cause I thought I lost a villager, but lucky I had backups just in case something bad happened to one of them, so I went back through 2O, out 2N, back to 1N to go out 1O, BUT when I went through 1N our to 1O, the missing villager was there parading around like nothing happened! It teleported to the wrong portal!
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This could be a residual effect of MCPE-125388, if going through the portal prevents the rider’s position from updating properly.
Or maybe MCPE-155678 was not actually fixed? I’m not sure what the scope and reproduction steps of that one were.
I can confirm 3 distinct nether portal bugs in 1.19.0, but none of them quite match this report.

Is this still happening in 1.19.0? I have not been able to reproduce as yet.

I haven't played since 1.19 came out, so I really don't know, but I will try to reproduce it later today too see if it happens again or not.

Thanks. In the meantime I've reverted the summary (title) of this report to the version that better matched your description, since I've been able to split out other distinct issues with nether portal transport.

Would you like me too upload pictures of the portals/surroundings of the portals when I get on? Would that help?

Yes, please do.

So I tried a couple of times today, replicating that day the best I could remember and I wasn't able to reproduce said event. Also added the pictures.

Thanks for re-testing. I am going to resolve this report at "Cannot Reproduce". If you have further issues with sending mobs through nether portals please check if they fit the reports I've linked to this one as "relates to".