Double tap Crashs IOS App

hi, 
i just bought the iOS app of Symphony Pro. On my IPhone 8.
it looks nice, but every time i want to edit a note afterwards and doing the “Doubletap” on the note I want to change, the App freezes and then completely closes and everything I have done until then is gone when I restart the app. 
I did reinstall the app and rebooted my phone, nothing helped. And I couldn’t  find any answer to this issue on the web?

i hope some of you can help me! :)

kind regards,
Katlar