Got your cohost ask.
Unfortunately asks aren't DMs, so the only way to respond to one without blasting it to the timeline is basically send back a new ask to the person if they have asks enabled.
Anyway, not relevant to your problem.
Which version of HammUEr on which version of UE4 are you using?
What kind of map format are you trying to import?
With what kind of texture sizes?
I'm guessing you don't have a repeatable repro case that I can try here, where you have a single map that has misaligned textures every time it's imported...
But yes, screenshots and map snippets would help, but if there's no repeatable thing (even if it's "every 50th time I import this file", that's fine), it's unfortunately going to be very hard for me to try and figure out what's wrong, besides "there's a sneaky error in the math, somewhere" which doesn't really narrow it down.