Yugo's are my favorite SKS rifles & they are nice guns with quality machining but have a lot of shit that can go south. Mainly it's corrosion and, of course, abuse, that starts the decline.
Check the gas port/gas plug. They can leak but can be wecsog'd with a paperclip gasket. If that doesn't work, there are 3rd party vendors that sell oversized replacements. (Murray's Guns).
The cutoff valve can get screwed. The can become a PIA to move if the components are out of spec.
The bolt face may be of a weaker steel and possibly prone to "volcanoing" (peening), This may or may not lead to popped primers which may or may not lead to slam fires. Primer chips have jammed a firing pin...you don't want this.
Cosomoline....clean all of it, especially the firing pin channel. That gummy shit will turn to rock hard varnish when heated and it will ruin your day if not your gun. I used simple green, hot water & elbow grease.
All in all, it's a chunky, bad assed goofy cousin of the SKS family. Enjoy!