Am I correct in presuming that these are export files from Microsoft OneNote?
My research suggests that the process is not 100% foolproof.
There is the possibility of having problems importing if notebooks are too large or too complicated or have certain complexities in them that we're not anticipated when creating the import tool.
If it is the import tool that's scanning your data and crashing that is I think more unfortunate than if it could give you the option to skip the error and continue.
I came to Joplin from Evernote and had to deal with certain abnormalities when importing my data. Not 100%.
ANOTHER OPTION
You can try one of these converters.
onenote2md
Jimmy (cross-platform converter) – Converts many note formats (including OneNote exports) to Markdown.
- Use an Online Converter (Works on Android Browser)
You can upload your OneNote .one or .onepkg file in a mobile browser and convert it to Markdown online:
GroupDocs ONE → MD Converter
A free web-based converter that takes a OneNote file and outputs .md files right from the browser.