Tis true most studies are uncertain. I think there are not enough people being tested so it depends. What if you test lets say bunch of guys who have foreign ancestry one or two ancestors behind. XD Specially problematic is SLO in this case where +20% are not Slovenes at all. However proximity with Hungarians dosen't strike me so much. It must be natural that we are close to them i guess. Especially cuz of their good deal of Slavic ancestry.

Scientists are very good at selecting samples. Often, they select subjects from villages that experienced least migrations. Out of the selected sample subjects are further narrowed down to eliminate any relatives from the sample.  There is a short description I pasted above explaining how scientists narrowed a sample of 996 to 178 subjects in Lusatian Sorbs’ study.
Most scientific studies are prone to errors.  One of the reason these studies are published in peer review journals often releasing  data so that other scientists can look and analyse the data replicating the results. It's always better to read several studies on a subject.

AFAIK in Yunusbayev  et. al study I mentioned above others found several subjects to be related which is mentioned in their errata.

Hungarians would not be genetically very different to their neighbours. It's a common trend in many regions of Europe.