wierd image problem, 403 Forbiden

I’ve migrated site from one server to another.
I’m not a beginner, I did same thing more times I can remember, but never I did encounter problem as such:

Images are sometimes showing and sometimes not, in a random fashion. Sometimes images are partially shown, different ones each time.

Permissions are set as recommended, settings are updated in config file and in database.
.htaccess – is ok, turned it off and on – same result

sometimes page renders itself “403 Forbidden” – after couple refreshes
(if I refresh it after 10sec it works again???)
sometimes page gets loaded without style

Here is a link to site: please change “,” for “.”
https://78,46,187,34

I don’t know what else to check, it must be gremlins…