Help - Font changes weight on opposite page when using transparency
When I place a transparent rectangle behind some text, to make it more readable, the font of the text on the opposite page changes in weight.
It's not only a preview error in InDesign, because when I export it as a PDF the difference in font weight remains visible.
This is without the transparency:

This is with transparency on the left page, and the font weigth on the right page changes.

On the next spread, the font is normal again.
The font I use is Jost.
Why does it do this and how can I fix it?
Please help.
Kind regards