Hi there, fairly new to TS Classic and been playing with Builder Route and Scenario Creation. I have the latest versions of Steam and TSC and DLC's all downloaded and installed in the last 3 months.
You must be sure to include the exact IDs of each tanker in the couple-to-front/back instruction. It's easy to make a mistake here as you have to keep track of where each car is as the scenario evolves in your head. Also choose the correct side front or back.
I just did a Free Roam by placing 4 different TEA tankers on different sidings Then using the Kuju 37 I was able to couple the wagons together and shunt them. But this is without instructions - just running in sidings - so wagon numbers are not used I suspect it might be something to do with the coupling instructions - coupling front or rear of the loco? I don't have a scenario that involves coupling of the TEA tanks to try.
Not being able to have a look at the scenario, I'm pretty sure your couple-to instructions are wrong.
I was a box lad at Stockport 72-74, Guide Bridge Guard 74-76, Piccadilly Guard 76-92 then went Driving. In 2002 I moved in to Northern's planning office due to health reasons. Retired in 2016 after 44 years.
It's nice to know that TSC has sufficient authenticity to interest retired railwayman. I guess it's not exactly the same, but presumably it has enough to bring back happy memories, or to allow what-iffing of some of the mad things you will have no doubt seen in many years on the railways! It's interesting, but despite the rotten hours, dirt and tedium, many ex-railway men (at least on the internet) seem to have happy memories of their time with BR. I get the sense they had a feeling of being part of something bigger, and had pride in a job that other people depended on.
Glazebrook Tanks unloading? When I was in the Box at Edgeley 2 in 1973 the tanks came off the Northenden line as 6E93