I notice that "service loses and gains coaches" at Elford. What might that have been, I wonder?
I noticed that too and guessed that it was just a RTT glitch
RTT is just repeating the activity code entered in the planning system and then uploaded to TRUST. RTT has interposed 'coaches' for 'vehicles' though. Activity codes are shown at stops to tell the various systems what the train is doing at that location (e.g. T for 'Train stops to set down and take up passengers' or L for 'train stops to change locomotives'). This makes sure that e.g. passenger info systems suppress set down stops, ARS holds the train to be overtaken, or TOPS expects a change in train formation.
Activity code '-T' meaning 'Train stops to attach and detach vehicles' is the default code for a stop in most non-passenger train categories. A planner (TOC or NR) when creating or amending the schedule has overlooked the code, or forgotten to put the '*' in first place on the activity code list to suppress the code when sending it downstream. It's very easy to do.
At Tamworth the 'S' code automatically suppresses the -T code for sending downstream. All of this can be read in section 1.3.5 of the TPRs (although some regions have a simplified version, NW&C at least has the full version).
(It's the same reason passenger trains sometimes show stops at junctions, the default code for a passenger train is 'T', and must be manually overridden).