pigman will randomly become argovated without being hit

when in the nether zombie pigmen will change from being passive to aggressive without being hit. i confirmed it is a bug by isolating myself in a 50x50 are covered with half slabs to prevent spawning and walled in on all sides and waited 10 minutes standing in the center. when i went back out i passed several passive pigmen and then had one a few blocks in front of me turn around and charge me with being attacked. This issue has made the nether untenable for me to traverse even in diamond armor with a diamond sword