Cursory

I never use enroute section but I do use navigraph charts and I had issues when using liveries and didn't when using the all-white livery, this does not necessarily mean anything but I observed consistent crashes and it just working based on if I am flying a livery or all-white. I am still thinking it's the liveries that are involved somehow and maybe even multiple systems contributing to these crashes.

Update: I just finished a flight with the A350 from gate to gate without issues when flying the all-white livery again so I am 99% sure that the WTF.dll crashes are related to the liveries. I haven't tried flying the inibuilds house livery but it either crashes because it is a livery being applied to the default white one or it doesn't crash because it was included with the plane installation and is not a separate instance. If immersion is everything to you don't fly the A350 for the time being, if you don't care: fly the all-white livery and default sim nav data to be on the safe side.

I can pretty much confirm that reinstalling the liveries and then flying with one just causes the WTF.dll module to crash again flying the same route I flew yesterday with the all-white livery without issues.

The all-white livery is what I found resolved the wtf.dll module crashing for me. The only thing I would suggest is a full reinstall if you haven’t tried that already because what you are describing is not what I have seen or heard of until now so nothing as far as I am aware is known about the issue you are having.

I believe I've identified what’s causing the WTF.dll module to crash, and here’s how I came to that conclusion: Yesterday, I began running test flights: I completed a ~3-hour flight in the -900 variant using the default sim NAV data and the all-white livery. The flight went smoothly from gate to gate with no issues. I followed up with a much longer ~8-hour flight in the -1000 variant, which ended up lasting nearly 10–11 hours total. This time, I used NAVIGRAPH navigation data, but again stuck with the all-white livery. No issues or crashes occurred. Today, I decided to fly the FINNAIR livery from Helsinki to Tokyo and during this flight, the WTF.dll module crashed again. While I can’t be 100% certain yet, the pattern suggests that the crashes may be related to liveries, not the navigation data or aircraft variant. I haven’t yet reinstalled the liveries (since I doubt it’ll change anything), but I’ll try that next and share an update tomorrow. In the meantime, I recommend that anyone experiencing similar issues try flying with the all-white livery, even if it breaks immersion. At least that way, your aircraft should remain functional.