When playing 18EU there is two major flaws.
If on corporation have for exampel one 3-train, one 4-train and a pullman, and another player buys a 5-train, the company with two trains plus a pullman gets his pullman discarded and is also by the program forced to discard one of his other trains as the program still thinks he has 3 trains. The result? Just one train left for the poor corporation.
Major bug number two in 18EU is: When someone buys the first 8 train there is no more of them available. There should be an unlimited number. This results in that there are just six trains left for eight corporations. Three 5-trains two 6-trains and one 8-train.
I have moved the second bug to a new Bug Report, as it is a separate issue.
I have also changed the Summary (which was: "Problems when buing trains in 18EU")
I have tested this with version 1,0.6 and with the current version, and in both cases only the Pullmann was discarded.
I cannot further pursue this problem from the currently available information.
A save file from the game in question would be helpful.