Can confirm this occurs on the main release channel and also RC.
This sometimes happens just when loading a page for the first time but also occurs when your cursor is over top the image. Clip demonstrating that on the same site as emzoumpo
And below you can see this happen on cbc.ca with Orion RC
Currently testing on:
Version 0.99.123.3-beta (WebKit 622.214.171.124)
Version 0.99.123.3.5-rc (WebKit 6126.96.36.199)
MacBook Air (macOS Ventura 13.4 beta build 22F5027f)
However, this also occurs on Ventura 13.3 with 123.3-beta