If the website has several languages (Polylang), and language versions of the tabs have been created, then for some reason the last activated/saved language version is displayed on the product page, and not in the desired language.
For example, if the site has three languages, two of them are Ukrainian and English.
So if the English translation is activated/saved last, then on the Ukrainian product pages the tab will be displayed in English, although it should be displayed in Ukrainian (and vice versa).
PS. There is no such problem with Legacy tabs and the use of HTML Blocks. I cleared the cache, it is not because of them.