Restoration Magic Cure tier for 0 mana plus 1 base cost doesn't have priority. Numerous games versus green or red decks (no "Nowhere to run" on the field or in these decks).

I hold 1W mana for the base cost of restoration magic - cure tier costs 0 for hexproof/indestructable. Then an opponent casts an instant targeting my creatures (for example green target own creature deals damage to opponent creature, and basic red burn spell for 2-4 damage)

It doesn't allow me to react, despite having the mana, not pressing spacebar to skip phase and no auto skip on phases. It doesn't always happen, but probably 1 out of every 5 uses and I cannot figure out why.

This also happens when using "defend the rider" instant 1G - choose one
Give target creature hexproof/indestructable or create a 1/1 crew token. I often times don't get priority to react or use the hexproof when targeted despite having available mana.