Bitmap text scaling problem

• Flixel version: 4.0.1
• OpenFL version: 3.6.1
• Lime version: 2.9.1
• Affected targets:
  Windows, Android, iOS

Code snippet reproducing the issue:

package ;
import flixel.FlxG;
import flixel.FlxSprite;
import flixel.FlxState;
import flixel.graphics.frames.FlxBitmapFont;
import flixel.math.FlxPoint;
import flixel.system.scaleModes.PixelPerfectScaleMode;
import flixel.text.FlxBitmapText;
import flixel.text.FlxText;
import flixel.util.FlxColor;

class TestBitmapFont extends FlxState
{
    var text:flixel.text.FlxBitmapText;
    var text2:flixel.text.FlxBitmapText;

    override public function create():Void
    {
        FlxG.mouse.visible = true;

        //The problem happens with any scale mode
        FlxG.scaleMode = new PixelPerfectScaleMode();

        //The problem happens with any combination of these settings
        var ppPosition:Bool = false;
        var ppRender:Bool = false;
        var aa:Bool = false;

        FlxG.camera.antialiasing = aa;
        FlxG.camera.pixelPerfectRender = ppRender;

        //Any non-antialiased pixel font can be used here
        var font = FlxBitmapFont.fromAngelCode(AssetPaths.pixel_mid_32__png, AssetPaths.pixel_mid_32__fnt);
        text = new FlxBitmapText(font);
        text.setPosition(10, 100);
        text.autoSize = false;
        text.width = text.fieldWidth = 500;
        text.alignment = FlxTextAlign.LEFT;
        text.text = 'Medium font, scale : ${text.scale.x}';
        text.color = FlxColor.fromInt(0xffffc600);
        text.antialiasing = aa;
        text.pixelPerfectRender = ppRender;
        text.pixelPerfectPosition = ppPosition;
        add(text);

        //Any non-antialiased pixel font can be used here
        var fontB = FlxBitmapFont.fromAngelCode(AssetPaths.pixel_tiny_16__png, AssetPaths.pixel_tiny_16__fnt);
        text2 = new FlxBitmapText(fontB);
        text2.setPosition(600, 100);
        text2.autoSize = false;
        text2.width = text2.fieldWidth = 500;
        text2.alignment = FlxTextAlign.LEFT;
        text2.text = 'Small font, scale : ${text2.scale.x}';
        text2.color = FlxColor.fromInt(0xffff5d37);
        text.antialiasing = aa;
        text2.pixelPerfectRender = ppRender;
        text2.pixelPerfectPosition = ppPosition;
        add(text2);
    }

    override public function update(elapsed:Float)
    {
        super.update(elapsed);

        //Scaling controls
        if (FlxG.keys.justPressed.UP) {
            text.scale.set(text.scale.x + 0.2, text.scale.y + 0.2);
            text.text = 'Medium font, scale : ${text.scale.x}';
        }

        if (FlxG.keys.justPressed.DOWN) {
            text.scale.set(text.scale.x - 0.2, text.scale.y - 0.2);
            text.text = 'Medium font, scale : ${text.scale.x}';
        }

        if (FlxG.keys.justPressed.LEFT) {
            text2.scale.set(text2.scale.x - 0.2, text2.scale.y - 0.2);
            text2.text = 'Small font, scale : ${text2.scale.x}';
        }

        if (FlxG.keys.justPressed.RIGHT) {
            text2.scale.set(text2.scale.x + 0.2, text2.scale.y + 0.2);
            text2.text = 'Small font, scale : ${text2.scale.x}';
        }

        //Changing position sometimes introduces artifacts (??)
        if (FlxG.mouse.justPressed) {
            var pos = FlxG.mouse.getWorldPosition();
            text.setPosition(pos.x, pos.y);
            text2.setPosition(pos.x, pos.y + 50);
        }
    }
}

Observed behavior:
When any scaling happens, the text becomes non-consistent - some parts get unproportional scaling, i.e. vertical or horizontal lines are sometimes thicker / narrower than they should be:

Expected behavior:
All parts of the text should scale consistently.

Start by reproducing the behavior with the provided TestBitmapFont example, then trace the FlxBitmapText and FlxBitmapFont rendering path under different scales and pixel-perfect settings. Done means bitmap text scales consistently without thicker or narrower lines across the listed targets and configurations.