Frankiek,
Slice up this Ju88 Pack into it's pieces, that's the only way to track the faulty class.
That's how I mod my custom BAT: When I trace a Mod Multi Slot Pack faulty,
it's mostlikely some corrupt class, hard to track.
By slicing it up, i.e. having each Slot, you track the glitch better.
Installing fixing this large Pack, is sth. I would spare myself. You loose
overall sight too soon. Make it simple.
Dump of your Mod Game Base:
Java and 3-D Files
Resolve all classes from this Mod
look up their codes. Maybe you find pieces of Java not utterly needed.
You must decide yourself, trusting your instincts.
Trial and Error is the way.
Sometimes you trace potential Errors on the run. (Paintscheme Java, ...)
If not start slicing, take each Slot out and start adding, Slot after Slot, one by one.
Fixing 1 Slot is easier. The Log is more precise.
If you're 100% sure the first Slot must be working and still throws errors.
There's sth. in the current code that's different to your Mod Game base code. That is my experience.
To cross check, take a similar Slot and use their Cockpit, remember to check
Slot dpendencies in Cockpit and Motherclass. Sometimes a Cockpit has a specific Slot call.
That way, by using a 100% method, you can apply for every other Part as well.
That's the basics of fixing such nasty Buggers.
It eases up Bughunting. By slicing up the Slots, you learn about them, what parts they used.
Then ask yourself can that work, see if it works.