Hi, it seems like all this problems was caused by this:
https://github.com/joomla/joomla-cms/issues/7316
The change in Joomla! which caused it, will be set back, so it will work the same way like in past
Regarding documentation:
1) first, this change was caused (probably) by upgrade from Joomla! 3.4.1 to Joomla! 3.4.2 - in fact this problem still searches its solution so it is hard to give any advice there when it is not finished - for not it seems like in next version of Joomla! the change will be set back so it will work the same way like in past - so this cannot be mentioned in documentation yet, as this problem was caused by change which is not related to Phoca Download
2) anyway, regarding documentation, see:
https://www.phoca.cz/phoca-needs-your-help/
Please let me know if you have upgraded Joomla!, if yes, then this explains it all.
Anyway thank you for the info about this problem, this was very useful as I was able to detect places which were influenced by this Joomla! change.
Thank you, Jan
Quick solution for now (until it the feature will be set back in Joomla!), see:
viewtopic.php?f=1&t=34527#p113076
(This is guide for Phoca Gallery but it is the same for Phoca Download)