dinasset, with your 2nd:
1st execution of the filter with default values: no problem.
I changed the size and height, I put these parameters:



and I did have a mosaic but with these messages:



Edit: I'm going to stop for tonight because I haven't had dinner yet!

I tried with your indicated changed values and I had no problems.
My only guess is that you relaunched the filter on the output of previous run, maybe...

dinasset, I just started again and no problem by calling the filter several times in succession by Bestfilters, (and not by Filters / Repeat).
Edit:
@ JappaloefFinally, your "Shine" was more recent than the one I got here: http://gimpchat.com/viewtopic.php?p=242117#p242117
thanks again!