Thanks Alfg for your input, after Paul’s and your posts, it was clear that the problem is on my side and not in the Jaikoz app.
I uses to drag and drop folders to Jaikoz from Total Commander - it’s more practical than using Open folder command, especially when you have a multi disc album and Jaikoz cannot identify it as a whole, only if you insert them disc by disc.
I still don’t know what happened but my solution for this problem is to run Total Commander with admin rights.
So, with Total Commander running as admin, drag and drop works, with Total Commander running in normal mode, drag and drop doesn’t work, on my setup ofc.
Just wanted to thank you and let these here if someone else with a similar problem is looking for a solution.