http://files.[ simutrans [dot] us (site down, do not visit) ]/files/get/osZovy_gLW/simscr18.bmp
Certain rail tiles disappear on the season update. Going into underground mode and back (!) makes them reappear. I'm guessing there's a rendering order issue during the season update or something? Note that this is a self-built pak.britain.experimental and the rail is Wrought Iron (in case it's a pakfile issue).
I have that same problem with official 8.2.
I think james suggested it might be a problem with the standard nightly experimental was compiled from.
Hmm, well, I'm getting this in -devel, so it's a bug in the codebase. Can someone check to see if there are problems like this in 'standard'? If not, it's probably due to a bad merge from standard (the divergences are getting very serious, I really need to try to get rid of as many as possible).
I have this too (using 8.2 & pak128.Britain 1.07 std). To me, it seems it only happens to some diagonal snow-covered tracks.
Thank you for your report. There are no changes at all to anything relating to graphics rendering in -Experimental, so, unless, as far as I can see, very improbably, this is a very odd and remote side-effect of some change to something other than graphics in -Experimental, this is a problem in -Standard, too. Can people check to see whether this can be reproduced in Standard?