Igniton problems 2010 1.6 TDI

The car in question is a 2010 Octavia 1.6 TDI with 95000 km on the clock

It all started about a year ago when it randomly wouldn't ignite and the starter motor was just spinning. It usually started the second time I tried, but when it got going it sputtered a little the first 1-2 seconds. This happened maybe 1 out of 5 times, 4 out of 5 times it fired right up without any problem. I changed the battery but it didn't help. Then came winter, it gets pretty cold here in Norway so new problems often come to light in -20C and this was exactly the case. A new (and worse) problem reared its ugly head, the car started but immediately stopped. When it was around -10C or colder the engine ignited right away but it died down before I could do anything. The revs jumped to 1200, then fell to 600 for maybe one second and then it died. This car has automatic disengagement of the starter motor so I couldn't help it get going that way either, mildly frustrating. It did start when the auxilliary heater had been running for some 20 minutes though, that was until the heater stopped working. I delivered the car to the dealership thinking the glow plugs were the problem, but they didn't find any fault codes and adviced me to remember to wait until the glow plug light went out before starting it. Wow, great advice, never thought of that... for the record it had absolutely no correlation with if I pre-heat the glow plugs 1 or 5 times, the result was always the same when it was really cold.

Then with warmer temperatures the car was fine all spring until lately. It was 25C and the starter motor was just spinning without ignition again. It started on the third try but suddenly when I was driving it went into some sort of emergency mode. It happened as I dropped it into 2nd at about 1400 rpm, just as the turbo spooled up the engine suddenly hit a new (and very very low rev limiter) at about 1600 rpm. The yellow glow plug light was flashing (which means engine management problem) and a bit perplexed I kangaroo skipped into a parking lot. I restarted the engine and it was almost normal but didn't rev smoothly at first. After restarting it again it was normal again. Drove to a dealership and they could get me a diagnostics appointment in 3 weeks, excellent service... I had to move across Norway the same week so I drove 700 km of mountain passes with maybe 400kg of load a couple of days later and the car was just fine.

Now waiting for my service appointment I just wondered if anyone has any idea what the problem could be? This forum has saved me a lot of money before when I had a good understanding of what could be wrong so the workshop didn't get to go ham with their troubleshooting. If it is an EGR problem shouldn't it be more of a constant issue? I've been doing some reading in other threads and I see that the exhaust pressure sensor might cause some similar symptoms, at least with the emergency mode. Any input is greatly appreciated!

I see this got a bit longer than I was planning for but I hope at least someone can get through this wall of text of English-ish with Norwegian syntax