numbers app (on iphone) fails to access(open) a dropbox cloud-placed tablefile

Hello community

Someone experimented already the effect described in the "subject"?

(User logout effect when apple's app "numbers" (on iphone) tries to access (open) a dropbox cloud-placed tablefile)

-I'm logged on dropbox app on iphone; on the dropbox cloud I have a file of calculation type (apple's "numbers") and which I see from the dropbox app 

-After starting the numbers app I can navigate to that table file for opening BUT 

-Immediately I get a popup from numbers app saying "table deleted. this table was deleted in other place" and I'm invited to re-submit the authorisation procedure

-Back to the dropbox app I see me logged-out with a popup "logged.out. <user> has been logged-out on this iphone" and I have to re-login

Any good idea, how to get rid of this problem? I suppose there is a security and/or permission issue.