packages/devextreme/js/__internal/ui/date_range_box/strategy/rangeCalendar.ts:196

• value[0] is a DateLike (can be 0), so a falsy check incorrectly treats valid timestamps like 0 (Unix epoch) as “missing”. Use a nullish check instead.

This issue also appears on line 215 of the same file.
packages/devextreme/js/__internal/ui/date_range_box/strategy/rangeCalendar.ts:219

• This condition uses && value[0] which treats valid DateLike values like 0 as absent. Prefer a nullish check so epoch timestamps don’t skip the out-of-range correction.

packages/devextreme/js/__internal/ui/overlay/overlay.ts:936

• Same generic type mismatch as above: pushing this into Overlay[] may be a TS error if Overlay<TProperties> is not assignable to Overlay<OverlayProperties>.

Cast this to the stack element type (or adjust OVERLAY_STACK typing).

    if (!isInStack) {
      this._zIndex = zIndex ?? zIndexPool.create(this._zIndexInitValue());
      overlayStack.push(this);
    }

packages/devextreme/js/__internal/ui/overlay/overlay.ts:922

• Same generic type mismatch as above: overlayStack.indexOf(this) may be a TS error if this (Overlay) is not assignable to Overlay<OverlayProperties>.

Cast this to the stack element type (or adjust OVERLAY_STACK typing).

  _updateZIndexStackPosition(pushToStack: boolean): void {
    const overlayStack = this._overlayStack();
    const index = overlayStack.indexOf(this);
    const isInStack = index !== -1;
    const { zIndex } = this.option();

packages/devextreme/js/__internal/ui/drop_down_editor/drop_down_list.ts:221

• _initContentReadyAction assigns to this._contentReadyAction, but the class does not declare _contentReadyAction. Without an existing declaration on DropDownEditor, this is a TypeScript error (property does not exist) and will break compilation.

Declare _contentReadyAction on DropDownList (or move it to the base class if it is shared).

  _initContentReadyAction(): void {
    this._contentReadyAction = this._createActionByOption('onContentReady', {
      excludeValidators: ['disabled', 'readOnly'],
    });
  }