Hello Dimiter, thanks for replying.
The situation we have is basically what I try to describe in the following dojo example:
Of course, this is a simpler version. In my version I have a remote datasource for the grid (from database, via a read action from an MVC controller). Each column that would be filterable with multi box does also have its own MVC read action datasource (pre-filtered to show only distinct elements and so on).
We have been able to pinpoint the issue and we have concluded that the error presents itself only on the multibox filters for columns, when the grid is loaded from a previous save. The error is restricted to columns with a remote datasource. I tried defining static datasources for some columns and they didn't experience the issue.
In this example, I tried to mimic a remote definition via the ContactName column, however, it is working properly on the example (I assume it is because I'm using the same source from your online data samples, not sure how to define a different one in this case). The only difference of this example with our problem is that the data comes from a different datasource than that of the grid, for each column.
Any ideas would be greatly appreciated, since right now we are sort of leaning towards removing this feature entirely or just using static filters for some of our fields, which is not a satisfying solution.