Libre Office: replace images by drag-and-drop doesn't work any more

Since upgrade from Ubuntu 18.04. LTS to 20.04 LTS, Libre Office misses the following feature: by dragging a picture from the file manager into a Libre Office window, and dropping it over an existing image, that image is replaced while preserving its size and position.

Steps to reproduce:
1. Open Libre Office Impress or Draw window.
2. Drag-and-drop a picture from the file manager to the Libre Office window.
3. Change the size and position of the picture in Libre Office.
4. Repeat step 2 (using the same or a different picture), dropping it over the existing one in the Libre Office window.

Expected result:
The picture is being replaced, but keeps its size and position.

Observed result:
The picture is added to the Libre Office window, while the existing one is not changed.

Workaround:
Right-clicking on the picture + "Replace..." gives the desired behavior. But is significantly more cumbersome, as one needs to navigate and find the correct picture with very small preview icons. It was much easier to do this from the file manager by drag-and-drop.

I use Ubuntu 20.04. LTS and Libre Office version 6.4.3.2 (Build ID: 1:6.4.3-0ubuntu0.20.04.).

I have checked the following:
- Booted Ubuntu 20.04 from a fresh Live CD: the error persists.
- On Windows 10 64 bit, using same Libre Office version, the behavior is as intended. So it seems to be an issue related not to Libre Office, but to the newer Ubuntu version, or its interaction with Libre Office.