Photo captions displaying vertically instead of horizontally on mobile/AMP

I’m contemplating installing the Mobile Theme and AMP plug-ins on my live site and have set up a staging version of my site to test this out. On my posts in the AMP version, everything looks good except for the photo captions – they are displaying vertically instead of horizontally. Any idea why? Example here: https://snipboard.io/6lhkbL.jpg

I have 10.3.9.1 installed – I was afraid to update to the latest 10.4 version after reading many of the comments on this forum, but I will try it on the staging site to see if this resolves issue without breaking my site.

I upgraded to 10.4, flushed WordPress cache and browser cache (Chrome), and the issue is still there. On the post I have mobile theme and AMP activated:
https://snipboard.io/IrAGWn.jpg

In the AMP settings I am in “transitional” mode, and these are the settings:
https://snipboard.io/JqUBhX.jpg

And in the Mobile Theme settings, these are the AMP-related settings:
https://snipboard.io/yAvHFn.jpg

Still getting vertical photo captions in AMP version:
https://snipboard.io/dDEb6Z.jpg

Any ideas?

• This reply was modified 5 years by pabucketlist.
• This reply was modified 5 years by pabucketlist.

Also, site health settings (and this is a staging site, not the live version of site):
https://snipboard.io/eUid7Y.jpg

I sent the requested info, but I also see one of your folks sent me an email with the following custom CSS for the mobile theme, and it worked to solve the issue:

.wp-block-image .aligncenter>figcaption {
display: block;
}