When first planned the MkV's were going to run the Scarborough and some Saltburn services to allow this it required overnight servicing facilities in Scarborough and York. Scarborough got built but due to the noise issues of the 68's the locals complained and TPE had to agree to stop using the site at night. York never got built.
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https://www.thescarboroughnews.co.u...victory-as-rail-operator-scraps-depot-3365213"
"TransPennine Express agrees to scrap overnight train storage in Scarborough after residents win noise battle
A rail operator has said it will no longer keep trains overnight at a new £7 million depot in Scarborough after local residents complained that the noise was making their lives a misery."
As such there is no overnight servicing facility in the east so you can't diagram the sets properly, the five diagrams they have require three of the sets to go on to the Scarborough site during the day, when they should be in service, so those diagrams are a waste. One only starts at 17:30 in the evening for return runs to Leeds and York, a total of 225 miles for the day.
Running to Cleethorpes/Hull would have caused similar issues so the only site you can use at night is Manchester Longsight which can't do all the sets. Hence the MkV's are a pain for TPE with the extra training requirements and the rest of the issues so with the planned service cuts the sets can be removed and costs cut at the same time.
Not sure but I don't believe 185's use the Scarborough site for servicing at present but that may change from December?