ARM performance degradation for a single ID

We are using ARM version 11.1.2.3.700 and, yes, we are expecting to be upgrading to the latest version by March 2019.

Over the past two months, ARM performance has degraded horrifically for the ARM administrator only. Field users do not have any issues, although, of course, the admin is performing different tasks.

As an example, the admin goes into transactions and expands Account ID in the left filter panel, then clicks on the filter icon, it takes as much as one hour to open the list box offering the list of items to filter!!! If I attempt this on my laptop with my ID, the filter list opens immediately.