Thanks to everyone hunting around for bugs! I truly appreciate the joined effort to help improve the application.
I've managed to squash a ton of bugs in this first minor release:

• Added missing spell sources. All spells up to MPMB v13.1.2 now export correctly
• Spells for which the source data can't be found (like homebrew) will still be added to the Actor's spellsheet
• Some errors contain more useful technical information (I will improve on this further in the next release)
• Fixed typo in XFDF text field
• Make XFDF parsing more robust when handling empty values (like an empty HP field)
• Fixed weapon range parsing for some weapons
• Fixed spellslots for all spellcasting levels being 0/0
• Empty biography entries don't have "Not found" text anymore, they're blank instead
• The name of the subclass is now loaded correctly for most classes (e.g. "Rune Knight" was previously shown as simply "Rune")
• Class features that are detailed in notes, but not in the class features list are now loaded correctly

There are some known issues that still persist that will need a bigger time investment from my end:

• Multiclass characters are not loaded correctly, will fix this in the next release
• AC calculation is not correct if the armor and/or shield are not added in the equipment list in addition to the Armor section
• AC calculation from passive effects like the Defense Fighting Style are not applied

Once the application is stable, I'm planning on adding some extra features. More on that later!

Keep being awesome and may the dice be ever in your favor.