https://snippet.dhtmlx.com/jprrqfmd
When a combobox is configed as readonly, “change” event will receive an event whose id is undefined. Although one can write a " if (id != undefine)" but I think this is a dhx’s mistake.
Could you please, provide the exact steps to reproduce the issue.
It is good when you first select whoever and seems sometimes it works well. Try to follow this step: Belarus -> Belgium. Looks like it appears when the second selection is diffrent from the first one.
Thank you for your clarification.
The problem is confirmed. It is related to unselecting the previous value before selecting a new one. We’ll try to fix it in one of the future updates.
Thank you for your report once again.
Your problem was fixed in the latest (7.2.1) dhx.Suite update.