I wonder if it is possible to correct this.
(https://www.mediafire.com/convkey/76dc/z25bxv3dajcbv406g.jpg)
Can you reproduce this with older revisions? I'm stuck at 7072, and have no such problems with bridges. So either it's an error in the bridge pak, or it's a recent regression.
It is present even in simutrans 112.3.. :o
Then it's a bug in the bridge. Contact the pak author. The most similar bridge in pak64 isn't perfect either, but not this bad.