I am having a totally bizarre issue with my Magic Effects...

I have two Mods, both of them add a new Constant Magic Effect of Restore Stamina; they are both added to an Ability given to the Player, with a quite high-value (they're meant to provide 'infinite' stamina). They both work, but... Not the same.

In Mod A, it results in the Player's Stamina never decreasing; so if I sprint, the Stamina bar appears, but does not actually decrease.

In Mod B, it results in the Player's Stamina freaking out; if I sprint, the bar will drop and refill over ~0.5, but once I stop sprinting, even if I am standing totally still and not touching any controls, the stamina bar continues to rise and fall rapidly for a good 20-30 seconds...

Both Magic Effects are identical. So are both abilities. But they're behaving completely differently on the PC.

I think this is also what's happening with another of my abilities--I have an old-ish mod that uses a 'Damage HealRate' Magic Effect to remove healing, but it is not working; the effect is set up perfectly, but is having no effect; I've even tried changing it to Damage HealRateMult, and still get the same issue...

It's like certain custom Magic Effects are not working properly, but only sometimes... :/

Edit:

I should add, I've already checked for Mod Conflicts; I've ran just Skyrim.esm, Update.esm and my Mod, and still get the effect; as I say, it seems limited to a small selection of Mods, rather than a thing across all of my Mods, which seems really bizarre to me...