Resizing subgrids not working for more than 2 subgrids

[taauntik]

Forum post

I'm having a small bug when resizing subgrids.
To reproduce the bug I used the "Big data set demo", where I created two subgrids (A and B) and populated both with some columns.

Resizing subgrid B seems to create no problems, neither when enlarging nor when shrinking.

While enlarging subgrid A (the leftmost one) I noticed that dragging quickly causes the resizing of the subgrid to stop (as if it lost focus).

When shrinking, the problem seems to not happen.

Here's the subgrid config

  subGridConfigs : {
      a : { width : 150 } ,
      b : { width  : 150 },
  },

and that's the column config

    columns : [
        { type : 'rownumber', region: 'a' },
        { text : 'Id', field : 'id', width : 50, hidden : false, region: 'a'},
        { text : 'First name', field : 'firstName', flex : 1, region: 'b'},
        { text : 'Surname', field : 'surName', flex : 1, region: 'b' },
        { text : 'Score', field : 'score', type : 'number', flex : 1, region: 'b'}
    ],

I didn't make any other change.
Can you help me with that?