Make sure that the appropriate paper settings for each tray is set to comply with the media being used.
Tap Settings on the control panel, then go to Paper > Tray Configuration.
Select which Tray the heavy card stock or labels are currently loaded, then go to Paper Size/Type.
Select the appropriate paper type currently loaded on the tray and tap Save.
If the issue persist, tap Settings > Paper > Media Configuration > Media Types.
Adjust the media texture setting to Rough and the media weight setting to Heavy. This will also slightly increase the fusing temperature.
For example; Cardstock - Texture (Rough) and Weight (Heavy) or Vinyl Label - Texture (Rough) and Weight (Heavy).