Male with X-chromosome matches from father's side? I am a male and in my FTDNA DNA-matches, when I filter for matches by X-chromosome match, I get around 30 people who can only be possible relatives from my father side (my parents came from distant European countries, the matches are from the region my father was born, and one of the matches is most likely related to my paternal grandfather. Is there a possible explanation or there's some kind of mistake in the test?

FTDNA will include segments as small as 1cM in X-matches; you'll need to compare in the chromosome browser to see how much you share with these paternal matches. If these matching segments on the X chromosome turn out to be very small segments, they're most likely Identical By Chance (IBC) and can be disregarded.