A support request, SR-B66277, was created by the user for this issue. A support representative will be in contact and tackle this issue with you. Any resolution will be added to this post once the SR is resolved.
This would appear to be that you are interacting with the combo box as it is being destroyed. Is that a possibility (i.e. the combo box is getting refreshed because you caused the page to change via a prior action)? If so, you might wait for the combo box to be destroyed while you are performing the previous step (and then wait for create) before interacting with it. You could confirm by placing a breakpoint before this step. By the time you hit it and continue, the control might already have re-loaded.