WordPress 5.4 & version plugin 5.136

Hello,

Could you try to delete the current version and install the latest 5.136 from the WordPress catalog? If the problem will persist please contact us by our private Ticket System for further investigation:

https://cleantalk.org/my/support/open

Yes, deleting and installing from scratch helped, and some caching protection was disabled

So the problem was resolved?

Hello, Yes. Russian saying: saving the drowning, the work of the drowning themselves)

Thank you for informing us.

Let us know if you have questions.