Spaceline reverts separator to default upon moving the window

[kGAr6Naaes]

Description

When Spacemacs starts I see the separator I set in .spacemacs
When moving the window Spacemacs inmediately changes the separator and the height back to the default

Reproduction guide 🪲

• Edit .spacemacs
• dotspacemacs-mode-line-theme '(spacemacs :separator arrow-fade)
• Save file and quit the program
• Start Spacemacs again

Observed behaviour: 👀 💔

• Separator arrow-fade is there after starting Spacemacs
• Move the window
• Default separator replaces arrow-fade

This also happens when opening any file

• SPC f f
• Default separator replaces arrow-fade

Expected behaviour: ❤️ 😄

• Move the window
• Separator defined in .spacemacs stays

System Info 💻

• OS: gnu/linux (Kubuntu 23.04)
• Emacs: 29.1
• Spacemacs: 0.999.0
• Spacemacs branch: develop (rev. b86a074)
• Graphic display: t
• Running in daemon: nil
• Distribution: spacemacs
• Editing style: vim
• Completion: helm
• Layers:

(html javascript rust python
      (auto-completion :variables auto-completion-return-key-behavior 'complete auto-completion-tab-key-behavior 'complete)
      emacs-lisp git helm multiple-cursors syntax-checking version-control treemacs
      (helm :variables helm-enable-auto-resize t helm-no-header t)
      helpful
      (org :variables org-enable-roam-support t)
      themes-megapack
      (auto-completion :disabled-for org git))

• System configuration features: ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM XWIDGETS GTK3 ZLIB

Backtrace 🐾

• None, Spacemacs doesn't throw any errors or warnings.
• There's no Warnings buffer on startup.
• emacs --debug-init doesn't throw errors or warnings.
• Combing through Messages doesn't show any package had an error.