Bug: display issue when dragging task from one group to another in Filter

i can reproduce this UI display bug quite readily. in the web view, suppose i am looking at a Filter that is configured to be a List grouped by something (e.g. Priority in my case). then i drag a task from Priority X to a different Priority Y. the issue is that the display of tasks in Priority Y gets messed up. the count shown to the right of the Priority Y label is correct, but one task is missing from what's shown. to fix this, i click Priority Y's dropdown arrow twice, and then all is well again.