I have reported about the disappearing of some nodes or a part of mind map a few months ago by email. Still this is happening very often and it’s is very annoying. I have also updated MN to the latest version. I am using the ipad version of MN.
I don’t know this only happens with relatively largely branched mind map.
Why can’t you give priority to solve this bug soon, as this is a major bug.
I can give you screenshots if you want.