I could not find a "Reading and Northern 19" but there are two "Reading and Northern" routes on the DLS
<kuid:279091:100003> Reading and Northern by Trainboy44422 uploaded 26-Feb-2014
<kuid:703507:100281> Reading and Northern by Aumant uploaded 10-Oct-2012
A missing thumbnail container is easily fixed by adding one to the config.txt file and supplying a suitable thumbnail. See
https://online.ts2009.com/mediaWiki/index.php/"Thumbnails"_container
If there is a missing texture file then there are two possibilities - either the file was removed by the creator because it was no longer needed but he/she forgot to remove its name from the config.txt file OR they forgot to add the texture file to the asset.
Texture files can be "tricky' because their name may appear in the config.txt file with the suffix ".texture" when in fact the full suffix is ".texture.txt"
You can try (after making a backup copy of the asset first) deleting any references in its confg.txt file to the missing texture file (.texture or .texture.txt) and see if that makes any difference.