The doors that swung in (for example on the Plaxton Interurbans) were far more reliable, another issue these huge plug doors have is that when it's windy they struggle to shut.
However these days the doors are less of an issue, the bigger issue is the use of coaches on local services like the X35/X36/X37. The coaches are not design for start stop work so the running gear gets worn out very quickly and they develop faults in mass. North Scotland for example bought 17 Interdecks in late 2015 for the Buchan Xpress network (Similar length routes as the X35/X36/X37, albeit no other competition) and by Summer 2017 most of the Interdecks were already mechanically worn out (or as the drivers put it 'past it'). Sadly now if you put one of the 08 plate E200s on a 63 along side the Interdecks, the E200 has more chance of making it back without faults. The issue with deckers on the 35 is the lack of toilet and the fact that some people may be travelling on the coach for 3+ hours.
I do agree that internally the E300s are not the best for the X35/6/7, however at a mechanical aspect they're perfectly suited and not being strained or out of their comfort zone at all.
The engineering effort at stagecoach in generally appalling across the board, I'm not surprised.
The implementation of coaches is a shaky idea, I get that, of course they make a statement which buses can usually match in more cases..
Aberdeenshire having the hills it does have should have coaches with Full-Autos, not robotised-manual gearboxes, only downside, volvo doesn't yet offer the ecolife with the 460 D11K engine even though it can cope with the torque now.
I think Volvo not offering the D13 for euro6 doesn't help matters either, but either way for such routes and stop-start these clutch
-boxes are a No no.
I'm certain VanHool for example now offers an allison T525R full-auto for the 510hp DAF MX13 engine.