Shifted Macro [Bug]

Describe the Bug

everything is compiles and flashes just fine, but after pressing the button - some OS things happen (muting sound and volume up (f13 f14)) but with shift (regular kc in upper layer) it's ok

System Information

Keyboard: dz60

Operating system: Arch Linux Linux 5.17.4-arch1-1 KDE 5.93.0 / Plasma 5.24.4

qmk doctor output:

➜  ~ qmk doctor
Ψ QMK Doctor is checking your environment.
Ψ CLI version: 1.0.0
Ψ QMK home: /home/chibo/qmk_firmware
Ψ Detected Linux.
Ψ Git branch: master
Ψ Repo version: 0.16.9
⚠ Git has unstashed/uncommitted changes.
Ψ All dependencies are installed.
Ψ Found arm-none-eabi-gcc version 11.3.0
Ψ Found avr-gcc version 11.3.0
⚠ We do not recommend avr-gcc newer than 8. Downgrading to 8.x is recommended.
Ψ Found avrdude version 6.4
Ψ Found dfu-util version 0.11
Ψ Found dfu-programmer version 0.7.2
Ψ Submodules are up to date.
Ψ QMK is ready to go, but minor problems were found
➜  ~

Any keyboard related software installed? no

Additional Context

yeah code is tough, that was hard work, mostly of ridingqwerty (https://github.com/qmk/qmk_firmware/issues/7839)

i see some progress, so i revisit it later, but if you help me organize it more simple way (like [declaration, [lower, upper]] w/o that low-level parametric stuff tap_code16(alt_keymap[1][keycode - AKM_1_8]); - i would be much appreciated

enum custom_keycodes {
    RUS_LAT = SAFE_RANGE, M_ARROW_RETURN, M_ARROW_FUNC, M_ASSIGN,
    AKM_1_8, AKM_1_9, MY_F13, MY_F14, AKM_2_22, AKM_2_23, AKM_3_11, AKM_4_11, M_CYR_ER,
};
// enum shifted_keycodes {AKM_1_8, AKM_1_9, MY_F13, MY_F14, AKM_2_22, AKM_2_23, AKM_3_11, AKM_4_11, M_CYR_ER};


uint16_t alt_keymap[2][10] = {
// AKM_1_8   , AKM_1_9       , MY_F13      , MY_F14        , AKM_2_22   , AKM_2_23            , AKM_3_11 , AKM_4_11    , M_CYR_ER
{KC_ASTERISK , KC_LEFT_PAREN , M_ARROW_FUNC, M_ARROW_RETURN, KC_LBRACKET, KC_LEFT_CURLY_BRACE , KC_COLON , KC_SEMICOLON, KC_M       },
{KC_AMPERSAND, KC_RIGHT_PAREN, KC_BSLASH   , KC_PIPE       , KC_RBRACKET, KC_RIGHT_CURLY_BRACE, KC_SCOLON, KC_BACKSLASH, KC_RBRACKET}
};

uint16_t key_timer;
bool process_record_user(uint16_t keycode, keyrecord_t *record)
{
  switch (keycode)
  {
    case RUS_LAT:
        if (record->event.pressed)
            {
                key_timer = timer_read();
                register_mods(MOD_RALT);
            }
        else
            {
                unregister_mods(MOD_RALT);
                if (timer_elapsed(key_timer) < 500)
                    {
                    layer_invert(RUS);
                    tap_code16(C(G(KC_NO)));
                    }
            }
        return false;
        break;

    uint8_t mod_state = get_mods();
    case AKM_1_8 ... M_CYR_ER:
      if (record->event.pressed)
      {
        mod_state = get_mods() & MOD_MASK_SHIFT;
        clear_mods();
        if(mod_state)
        {
          tap_code16(alt_keymap[1][keycode - AKM_1_8]);
        }
        else
        {
          tap_code16(alt_keymap[0][keycode - AKM_1_8]);
        }
        set_mods(mod_state);
      }
      return false;

    case M_ARROW_FUNC:
        if (record->event.pressed) {
        SEND_STRING("=>");
        }
        break;

    case M_ARROW_RETURN:
        if (record->event.pressed) {
        SEND_STRING("->");
        }
        break;

    case M_ASSIGN:
        if (record->event.pressed) {
        SEND_STRING(":=");
        }
        break;

  }
  return true;
};