Lidgar
Gongfarmer
It seems that your position is that the target could not use their action or bonus action, so they could not Dash at all then. The target could go through one closed door but not two, etc.
Don't really have a position about actions per se, was just pointing out that I think the intent of the spell is fail your save = lose your turn.
As others have mentioned, there is a plenty of room for DM discretion here. While I'd interpret spending it's turn moving away from you by fastest available means as using the Dash action, I could see circumstances, such as the gauntlet of seasoned warriors described up thread, where the Disengage action might be better. In either case, it moves the target away from the caster as quickly as it (safely) can.