To troubleshoot:
1. Check the main fuses: Start by checking the vehicle's main fuse box (usually under the hood or in the dashboard). Look for fuses related to accessories or the radio (the VHS player shares power circuits with these systems). Replace any blown fuses. If the problem persists, then it's not a simple fuse issue.
2. Check the in-dash fuse box (if applicable): Some vehicles have additional fuse boxes inside the cabin. Check there as well, but again, a blown fuse related to the player would likely cause a complete power failure, not just button malfunction.
3. Professional Repair: If checking the fuses doesn't solve the problem, the VHS player itself is likely faulty and requires professional repair or replacement. The cost of repair might exceed the value of an in-dash VHS player, making replacement a more economical choice.
In short, while checking fuses is a good first step in any electrical troubleshooting, the buttons failing alone points strongly towards a problem within the VHS player itself, rather than a blown fuse.