Big problem with Jetpack Gallery

Hello,

I just upgraded Polylang and I have now different problems with Jetpack galleries.
My setup:
Wordpress 5.5.1
Jetpack 8.9.1
Polylang 2.8.2

On some galleries, when we click on a thumbnail, the photo displayed is not the one that matches the thumbnail. For example: https://www.outofphase.fr/2018/04/05/fonctionnement-mellotron/
If I deactivate Polylang, it works perfectly.

On other galleries, when we click on a thumbnail, we have a black screen with comments section(?). For example, on this page, in the Photos tab: https://www.outofphase.fr/2018/06/21/birotron/
And impossible to leave the gallery. You have to reload the page.
Again, if I deactivate Polylang, it works perfectly.

At last, on all the English pages, the gallery don’t work anymore. When we click on a thumbnail, we have a black screen with comments section(?).

To confirm this problem, I deactivate all the plugins.
It seems there is a serious incompatibility between Polylang and Jetpack galleries.

Hoping that this problem will be solved quickly, because our site is no longer usable properly.

Thanks!

The page I need help with: [log in to see the link]