...
Test that the two gas sections are separated again. To do this, check that the He flowmeter is at a high value (it reads "H +F" above 500) and decreasing. The initial high value is because there is heavier gas (air) being purged out of the Front end / I0 section. It should eventually settle around 200-240 when only Helium is in the front end / I0 section. If the flowmeter value is already lower than this after clamping, this means there is a hole in the film. This often happens because the O-ring can cut the film. No worries! Just unclamp the assembly, replace the film, clamp and test again!
...