catflap This is "half" normal.
Until a while ago, on the left, there was a filter to display or not the "solo" videos, except that now it has disappeared, but those who had disabled the display of solo videos, well they have it in the bone because impossible to re-display the solo videos.
The option must always be activated in the database, except that we, fortunately, have no access to it, but when the option was removed, the work was half done because the database was not modified accordingly.
Fortunately, by going to the "category" solo, we have access to all the solo videos, but this is a "patch", it is not a normal use of the site.
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