Also when opening the editor, the font seems to have changed from helvetica to another one, looking much smaller and like a systems font. And strangely, here the captions of there images are still centered.
I fully tested the previous and latest WordPress and OceanWP updates but was unable to replicate the issue. By default, if an image block has no specific alignment set in the editor, aligns of the caption set to the left side.
Regarding the font change in the editor, it is likely a caching conflict.
Please try these steps:
I. Clear your website/server cache and CDN.
II. If you use Elementor, go to Elementor > Tools and click Regenerate Files & Data.
III. Perform a hard refresh: (Win: Ctrl+Shift+R / Mac: Shift+Cmd+R).
I tested again and and still in editor mode all captions are centered by default as before the update. But the published post renders them as left-aligned. Below a screenshot from the editor.