Hello, I have a question regarding funnel analysis in Amplitude.

I’m trying to measure a funnel with the following steps:

1. New user opens the app (start_session)

2. Sign-up process starts

3. Sign-up completed

4. A specific event occurs in the app

For step 1 (new user opens the app), since the user_id may or may not exist at this point, I applied a filter of user_id = none to isolate new users.

For steps 2 to 4, since these events are triggered by users who are logged in, I filtered with user_id != none.

However, I'm seeing an abnormally low conversion rate in the funnel.
When I check the 'View User Streams' feature, I can see that user_id is initially none at step 1, but it exists in the subsequent steps.

Why is this happening?