if a math region raises the error status, then is possible to resize the display bounds of matrices on LHS; this leads to strange behaviors while editing the region.
Steps to reproduce:
1) write omething like a*mat(1,2,3,4,2,2);
2) evaluate numerically [=];
3) move the mouse over the matrix -> now it is possible to resize the display bounds (content is still available as you can see using copy/paste) and is no more possible to resize the content of the matrix;
4) resize the matrix to 1x1;
5) try to add another matrix on the LHS (f.e. *mat(6,7,2,1)) -> the first matrix now displays all the values and is resizable, the latest seems an 1x1 matrix and inherit the resize issue (using copy paste, is a 4x4 matrix);