Librewolf throwing rebuild errors about backuping files

I recently wanted to change my librewolf setup to be incorperated into my nixos config. everything seems to work, except that i always get error messages like:

activating the configuration...
setting up /etc...
reloading user units for noof...
restarting sysinit-reactivation.target
the following new units were started: NetworkManager-dispatcher.service, searx.service
warning: the following units failed: home-manager-noof.service
× home-manager-noof.service - Home Manager environment for noof
     Loaded: loaded (/etc/systemd/system/home-manager-noof.service; enabled; preset: ignored)
     Active: failed (Result: exit-code) since Sun 2025-06-15 10:45:08 CEST; 267ms ago
 Invocation: b458b022f4204b4a8f98967faddd4a2d
    Process: 607430 ExecStart=/nix/store/8axxcgpnr78xkhy46yy2dxf5nwjwswv8-hm-setup-env /nix/store/35gcnc3izi4zkkjvv9h49s550ikxgnpr-home-manager-generation (code=exited, status=1/FAILURE)
   Main PID: 607430 (code=exited, status=1/FAILURE)
         IP: 0B in, 0B out
         IO: 0B read, 0B written
   Mem peak: 5M
        CPU: 240ms

Jun 15 10:45:08 cesium hm-activate-noof[607588]: - Move or remove the files below and try again.
Jun 15 10:45:08 cesium hm-activate-noof[607588]: - In standalone mode, use 'home-manager switch -b backup' to back up
Jun 15 10:45:08 cesium hm-activate-noof[607588]:   files automatically.
Jun 15 10:45:08 cesium hm-activate-noof[607588]: - When used as a NixOS or nix-darwin module, set
Jun 15 10:45:08 cesium hm-activate-noof[607588]:     'home-manager.backupFileExtension'
Jun 15 10:45:08 cesium hm-activate-noof[607588]:   to, for example, 'backup' and rebuild.
Jun 15 10:45:08 cesium hm-activate-noof[607588]: Existing file '/home/noof/.librewolf/main/search.json.mozlz4.backup' would be clobbered by backing up '/home/noof/.librewolf/main/search.json.mozlz4'
Jun 15 10:45:08 cesium systemd[1]: home-manager-noof.service: Main process exited, code=exited, status=1/FAILURE
Jun 15 10:45:08 cesium systemd[1]: home-manager-noof.service: Failed with result 'exit-code'.
Jun 15 10:45:08 cesium systemd[1]: Failed to start Home Manager environment for noof.

has anyone any idea what this means and why it happens?

here is my librewolf config:

{ pkgs, ... }:
let
  ublock-settings = {
    "uBlock0@raymondhill.net".settings = {
      selectedFilterLists = [
        "ublock-filters"
        "ublock-badware"
        "ublock-privacy"
        "ublock-ubreak"
        "ublock-quick-fixes"
      ];
    };
  };
in
{
  programs.librewolf = {
    enable = true;
    languagePacks = [
      "de"
      "en-US"
    ];
    policies = {
      DisableTelemetry = true;
      DisableFirefoxStudies = true;
      #BlockAboutConfig = true;
    };
    profiles = {
      main = {
        #extensions = {
        #packages = with pkgs.nur.repos.rycee.firefox-addons; [
        #ublock-origin
        #];
        #settings = ublock-settings; # use ublock-settings // other_settings to concat
        #force = true;
        #};
        isDefault = true; # selected by default
        name = "main";
        search = {
          default = "startpage";
          engines = {
            startpage = {
              name = "Startpage";
              urls = [
                {
                  template = "https://startpage.com/";
                  params = [
                    {
                      name = "q";
                      value = "{searchTerms}";
                    }
                  ];
                }
              ];
            };
          };
        };
      };
    };
    settings = {
      "accessability.blockautorefresh" = true;
      "accessability.browsewithcaret" = false;
      "accessability.browsewithcaret_shortcut.enabled" = false;
      "apz.enable_double_tap_zooming" = false;
      "browser.backup.enabled" = false;
      "browser.contentblocking.category" = "strict";
      "cookiebanners.service.mode.privateBrowsing" = 2;
      "cookiebanners.service.mode" = 2;
      "privacy.donottrackheader.enabled" = true;
      "privacy.fingerprintingProtection" = true;
      "privacy.resistFingerprinting" = true;
      "privacy.trackingprotection.emailtracking.enabled" = true;
      "privacy.trackingprotection.enabled" = true;
      "privacy.trackingprotection.fingerprinting.enabled" = true;
      "privacy.trackingprotection.socialtracking.enabled" = true;
      "browser.newtabpage.enabled" = false;
      "browser.tabs.allow_transparent_browser" = true;
      "sidebar.verticalTabs" = true;
    };
  };
}

thanks already.

I got the same issue. Thought it was bc I configured profiles.<name>.search.engines around the same time I got the error. Did your search engine config work before?