I have confirmed the issue. The steps to reproduce is the follows:

1. Create a project and add a user as a member of the project. Let's say this project as P1 the user's role in the project P1 as R1
2. Create another project and add the user as a member with another role. Let's say this project as P2 and the role as R2
3. Create a Spent time custom field and set the visibility of the custom field to only the role R1
4. Sign in as the user and navigate to the project P1. And then log time
5. Click "Edit" of the newly created time entry. You will see the custom field on the form
6. Change the project from P1 to P2 on the form. The custom field should disappear because the user's role in the project P2 is R2 and the custom field is not visible to the role R2. Actually, it does not disappear
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Felix Schäfer wrote:
> We think this should be changed to reload the whole time entries form similar to what is done for issue forms, see source:/trunk/app/views/issues/_form.html.erb@20821#L15
>
> Do you think this would be a good addition to Redmine or should this be done another way?

I created the patch with reference to source:/trunk/app/views/issues/_form.html.erb@20821#L15.
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