Change assignment does not auto populate the LOVs in when and why section - What's the way to change

In My client groups > Change Assignment > When and Why > what's the way to change the assignment - the LOVs appear only after we start typing, and does not get auto populated and for some users it is not populating even if they are typing.

Actions taken from our side - we ran the pre-requisites once again, checked and validated the profile options, and also ran the schedule processes, but the issue still remains.

Can anyone suggest a further action plan to solve this issue?

Note - this issue seems to be device specific as if we try to replicate it with the same user using our system, it works fine. Also it works one time and next time it does not.