Thx for the info. I will look into this issue. Some other Android users have also reported NFC problems, this could very well be the culpit. Probably I need to force NFC into the foreground
PS: Because I haven't set any default apps, whenever I click a link (e.g., in a message), I get to choose which app or browser I wish to use to open the link. In the same vein: When more than one app is able to read my passport over NFC, I would expect to see a list of possible apps.
There is now an updated version available on Google Play. I've tried to address these issues.