Ashtreegoat

I'm not sure how to check plugins or anything like that.... I'm not good with these kind of things. I (to my knowledge) haven't installed any plugins on this server.

I run a server with 2 other friends. I had OP-ed myself to turn on keep inventory as we kept dying and overall kinda suck at survival. My friends couldn't open certain chests and doors would glitch out when they tried to open them. Before I turned on keep inventory, this hadn't happened. I had to OP them so that they could play. I have no plugins installed in this server and have already tried disabling spawn protection, to no avail. Is there any way that I can stop this from happening so I don't have to OP my friends? It's not fun when they use their OP powers to cheat items and change time/weather settings. Any help would be appreciated.