Services across the network over the coming days may be subject to delays and short-notice cancellations due to a lack of available staff caused by industrial relations issues.
TPE state that
We are doing all we can to keep you on the move and, as ever, our aim is to provide you with a stable and reliable service as we know you put your faith in TransPennine Express to get you where you need to be.
We are sorry for any disruption this may cause to journeys in the coming days and ask you to allow additional time for travel and to check carefully – up to the last minute – for any changes to train times. You can check for updates on TransPennine Express services here: https://www.journeycheck.com/tpexpress/.
As a result of the ongoing issues, it has been necessary to make pre-planned cancellations to some services.
Link is Service Disruption | Travel Updates | TransPennine Express (tpexpress.co.uk)
The planned cancellations appear to change from day to day, so it is best to check online on the evening preceding .the day when you plan to travel.
This appears to be a dispute about rest day working and/or Covid-safe working practices, coupled with high levels of staff sickness/self-isolating.