Something that's affected me a few times now on leisure journeys on the south route is quite annoying, as TPE prefer to cut journeys short on this route once they are over 15 minutes late than continue a delayed service.
On Man-Cleethorpes journeys which might get delayed after leaving Manchester for whatever reason, and arrive in Sheffield over 15 minutes late, the service will end up terminating short at Sheffield, and the out of service train and same crew then continue the journey through to Cleethorpes minus the passengers. This most recently happened to me on Thursday when I was lucky enough (!) to board one of only 2 TPE services running from Man to Cleethorpes that day, the 0615. As the train was due to depart Picc the conductor announced signalling issues meaning it would no longer call at Stockport and take a different route. This led to us being stuck behind a stopper train and arriving approx. half an hour late into Sheffield. Once it became apparent the train was more than 15 minutes late we were told it would terminate at Sheffield. Arriving in Sheffield at approx 0735 the next running service to Cleethorpes was the 0911 meaning what would have been a roughly half hour delay became a much longer delay.
I've recently also waited for a TPE train Meadowhall to Cleethorpes, tracking it's journey on the TPE app as it came over the Pennines. Lo and behold, as soon as it was over 15 minutes late while over the Pennines (20 minutes in this case), the announcement was made the service was cancelled, the app showing the service terminating at Sheffield - but then running empty past me at Meadowhall continuing on to Cleethorpes without passengers 'due to a short notice change to the timetable'. In this case I only had a 2 hour wait until the next train so I was lucky.
Two different more senior colleagues have told me TPE will always prefer to cancel a service than have it running over 15 minutes late when possible as the 'penalties are lesser to cancel a train than have one running over 15 minutes late' with the public reason to always just put the 'short notice change'. This whole situation seems ridiculous to me, and only causes me frustration at having long waits for the next train. I've witnessed this happening behind the scenes at my own station in the north west, where services have been cancelled at very short notice rather than have them run 20 minutes late due to an alleged lesser penalty for a cancellation than a delay for the TOC, and the reason put out was a short notice timetable change.
I am unsure if this rationale applies only to TPE or if it goes off at other TOCs but I think cancellation penalties need to be increased from the DfT to prevent this happening as it only causes passenger frustration to see their train still physically running, albeit 20mins or so late, but not in public use.