Unable to remove slow wagon from consist

[Baldy's Boss]

I have largely converted the Charnston-Chinningdore route to Shinkansens with powered MU wagons.
However,when I try to remove a slower Talgo wagon from one of the trains to bring it up to the speed of the others,I get an error message.
They are of course from different NewGRF sets but what is causing the problem?

[vrn]

The issue seems to be the High Speed Mail Coach from 2cct, the other wagons can be removed after removing that one. That aside, I put some advice on how to increase the throughput of your station in the screenshot.

[Transportman]

I have largely converted the Charnston-Chinningdore route to Shinkansens with powered MU wagons.
However,when I try to remove a slower Talgo wagon from one of the trains to bring it up to the speed of the others,I get an error message.
They are of course from different NewGRF sets but what is causing the problem?

The 2cc Trainset has some checks on wagons, but it is not build against such mixing, so you might trigger strange behaviour.

[Baldy's Boss]

The issue seems to be the High Speed Mail Coach from 2cct, the other wagons can be removed after removing that one. That aside, I put some advice on how to increase the throughput of your station in the screenshot.

That enabled the speedup of the train,at the cost of mail capacity...as for moving the station,that would cost a substantial amount of the large buildings in the catchment area!

[Eddi]

you can add a bus stop to extend catchment area