[Bug]: Dragging and dropping a file into RV works very inconsistently

### What happened?

I was a bit torn on where to report this issue, because it has existed in RV for _many_ years (going back to at least RV 7), but it seems to have gotten much worse in OpenRV to the point where it's fairly unusable for our artists. This is a fundamental feature that our users rely on for their day-to-day workflows.

I'm generally seeing the same behavior between 2021, 2022 and Open RV which is: Quickly dragging a file from Dolphin (linux file browser) into the RV window often fails to bring up the drop target overlay. Hovering on the window makes no difference and still doesn't bring up the overlay. Dragging into the window slowly increases the chance of bringing up the overlay and that subsequent dropping then succeeds.

RV 7 can fail to accept the drop but only if you drag and drop the file very fast. The main difference seems to be that in RV 7 no matter what speed you drag into the window, if you just hover on the window, it brings up the drop target overlay, whereas RV 2021+ does not recover even when hovering. So it seems possible that somewhere between RV 7 and 2021, a hover event has been broken or removed which was previously showing the drop target. OpenRV seems to be more temperamental than 2021 and 2022... sometimes you end up only being able to drop right near the edge of the window where it activates the overlay as the overlay disappears once you move further into the window .

### List all the operating systems versions where this is happening

CentOS 7.8

### On what computer hardware is this happening?

Multiple configurations

### Relevant console log output

```shell
none
```

### Environment variables

_No response_

### Extra information

_No response_

### Code of Conduct

- [X] I agree to follow this project's Code of Conduct

Reproduce the inconsistent drag-and-drop behavior on CentOS 7.8 using Dolphin, comparing fast and slow drags and hovering near the window edge. The issue names no source files or tests, so first locate the OpenRV window drop-target and hover-event entry points; done means reliably showing the overlay and accepting the dropped file across the reported drag speeds.

Written by the indexing model from the issue text.