It's been about 5 years since I first got to see this bug in OOffice, and after moving to LO it's still there.
Changed computers and distros (now using MINT 17 x64 with LO 4.2.7.2 and this problem reappears every once in a while.
I googled this and found a few posts about it but since it's nowhere to be found here I decided to post this bug myself.
I can't recreate this bug, because I can't say exactly what causes it.
Didn't try in M$ cause I don't use it.
It happens every once in a while, and there is no way of telling it's about to happen.
What is actually happens is one of the following:
1. The content of a formula written using Writer's math editor disappears and I am left with a blank box.
2. The content disappears and the formula box becomes small, as if nothing was written in it.
3. The formula box becomes very small (as if it's empty), but its content is still there, only squished to the new size. When this happens, I can double click the box and sometimes the code is still there and I can copy it, delete the box and recreate the formula in a new box.

Last time it happened all I did was to hit the Enter key a few lines below the formula box, and the box went blanc.
(This should be in the most annoying bugs of LO...)
any other information needed from me will be happily supplied. :-)