Self inflicted debuffs

While I'm not 100% certain, I don't think debuff resistance offers any chances to resist self inflicted debuffs. Based off personal experience, Jeanne d'arc, one of my more frequently used servants, has a passive resistant to debuffs by 25%. Despite this, not once have I ever seen her noble phantasm's demerit of self stun been resisted, which is why I doubt it possible to resist self inflicted stuns through that manner. You can however complete nullify self inflicted debuffs with the Nullify Debuff status, like with Tamamo Cat's new skill strengthening of her Morph skill in the JP version, which gives her Nullify Debuff and therefore completely resists her self stun from her noble phantasm. Hope this helps :)

Probably would only work if it is a chance of self debuff, and I don't think any of those are worded as chance based. Debuff immunity might work.