Possible problems regarding security

Dear Team,
lately I experienced some problems with Gravity forms - people can't upload images anymore. I checked everything, but can't find a reason. Maybe a too tight security system... Before I installed Defender, I also had iTheme Security installed - this is still installed because I dopn't know what will happen if I deactivate that plugin. Now I wonder: is this too much, do these plugins interfere with each other? I must admit I lost my way with all these security gadgets..... Can you shed some light here?