Say a party of a Druid, Wizard and a Ranger REALLY doesn't want the creature to move during combat.
The Wizard casts Maximilian Earthen Grasp
The Druid casts Entangle
The Ranger casts Ensnaring Strike and hits the monster
Say the monster fails all three STR saving checks (let's say it's a mage with a usual weak STR score). So the monster will be Restrained at the same time by all those 3 different spells (say DC is 12, 13 and 14)
On the next turn, the monster tries to free himself and throws the STR save dice.
Our DM says "if the monster gets 15 on his STR save - he is "unrestrained" from all of the three spells at the same time, form that one good STR save." Basically his rationale is that in order to break free from all of the three spells the monster is spreading his arms and legs, pushing his body, etc. And this is the way the vines form both Entangle and Ensnaring strike break. So that one good push must break all of the vines, not just from one of the spells...
The other guy at the table says that the monster would have to make 3 separate STR checks, for each separate spell that restrains him. And actually the monster would require to spend 3 actions to get free from all the 3 spells. So that this nasty tactic would waste 3 precious turns for the monster.
Who is right by RAW?
How would you rule at your table in a situation like this?
Does this look like a smart move to ambush and neutralize a mage? Basically, cast two such "restraining" spells like Ensnaring strike and Entangle and then add a fog Cloud on top of it so that a mage can't cast misty step and will have to waste two precious turns to break free from all of the vines... Does that all make sense?