Getting into the operating theatre

Left of FRANK EINSTEIN, the floor corridor to the OPERATING THEATRE won't let Seymour through: he gets stopped at the same spot every time.
Nudge 1Where to look
That corridor opens only after something happens in the theatre. There's another way in.
Nudge 2A stronger push
Go in from above. The upper floor of FRANK EINSTEIN leads left too.
Nudge 3Almost there
The room above the theatre, THE VAN DE GRAF, drops you onto the theatre floor, and the operating table takes you back up.
What you needOther problems to solve first
Solve these first (each opens its own page, no answers on the way):
Show the solutionThe whole answer, with a video
From FRANK EINSTEIN's upper floor go left into the top right of the OPERATING THEATRE, on up into THE VAN DE GRAF and down onto the theatre floor. A studio key lies here (it opens King Kong's door in the maze). To leave, stand on the operating table: it's a lift back up. You can come and go this way as often as you like.
Why it works
The floor corridor holds Seymour in place until the monster has walked out of the theatre (The machine in the operating theatre); the upper route has no such check.