Can't update Flex User field from empty textarea

[Sogl]

I have some options:

• Account Type: Flex Objects (experimental) for Users.
• Session split false, one session for admin and frontend.
• Sync User in Session enabled (Login plugin).

I have some additional fields in my user\blueprints\user\account.yaml:

...
specialist:
    type: toggle
    label: PLUGIN_SOGLFLEX.ADMIN.USER.SPECIALIST
    highlight: 1
    default: 0
    options:
        1: PLUGIN_ADMIN.YES
        0: PLUGIN_ADMIN.NO
    validate:
        type: bool
        required: true

about_specialist:
    type: editor
    size: large
    label: PLUGIN_SOGLFLEX.ADMIN.USER.ABOUT_SPECIALIST
    placeholder: PLUGIN_SOGLFLEX.ADMIN.USER.ABOUT_SPECIALIST_PLACEHOLDER
...

These fields added to Login plugin registration fields:

I have user\pages\profile\profile.md for custom User profile frontend form. I added two fields:

...
specialist:
    type: toggle
    options:
        1: PLUGIN_ADMIN.YES
        0: PLUGIN_ADMIN.NO
    
specialist_check:
    type: conditional
    condition: "form.value('specialist') == true"
    fields:
        about_specialist:
            type: textarea
            label: PLUGIN_SOGLFLEX.ADMIN.USER.ABOUT_SPECIALIST
            placeholder: PLUGIN_SOGLFLEX.ADMIN.USER.ABOUT_SPECIALIST_PLACEHOLDER
            classes: input-lg
            rows: 7
...

And now the description of the problem. When I clear the about_specialist field from the Admin panel, it disappears in user.yaml file, it's fine. But I can't do this in frontend profile form, every form submit or refresh shows me initial textarea value. It's updated only if a value is specified in it, even a simple space.

Also, if I clear textarea in the Admin panel, the old value is still indicated when entering the frontend profile. It appears on every form refresh. Only the user's logout/login can clear this value (is it because the session is being recreated?).

I can't clear textarea value in frontend form. How to fix that?

[Sogl]

What I see using Xdebug on User save in Admin panel (parseRequest func):

Empty textarea parses as empty string. In frontend form it's about_specialist: null which is not included in the final request.