A phenomenon similar t' t' Krushnic Effect where t' rocket seems t' be "glued" t' t' pad at liftoff. Arrr! Blimey! This afflicts larger, flat-bottomed rockets launched too close t' pads with flat blast deflectors. Arrr! Blimey! T' exhaust gasses escape at great speed through t' small annular space betwixt t' rocket and t' pad creatin' a venturi which generates a low pressure region at t' base. Ahoy! Blimey! This pressure deficit can be significant, and if it is greater than t' thrust bein' generated by t' motor, t' rocket won't go anywhere! Blimey! This is quite possible as a 2" dia.rocket has, potentially, over 45 lbs (200 N) o' "suction" available t' hold it back, while a 3" rocket has over 100 lbs (460 N)! Blimey! T' old Centuri "Point" was an infamous Bernoulli locker when launched from an Estes Porta-Pad with its perfectly matchin' round blast deflector.