If you own a TC-WR535 which cassette decks won't open anymore, it's probably because the belts of the motor are in bad shape. I'm now gonna show you how to replace them.
Step 1: Tools you will need
These are the tools you will need:
a container for the screws so you don't lose them
replacement belts (2 for each deck, so a whole replacement set contains 4 belts, 2 small ones and 2 larger ones)
Step 2: Unscrew Part 1
Unscrew the 5 screws shown on the picture
Step 3: Unscrew Part 2
Unscrew the 5 screws on the bottom of the WR535
Step 4: Inside the TC-WR535
Now remove top part of the case and you'll see the guts of your cassette deck.
Remove the four flat cables (one on each deck, one small and one big in the middle)
Step 5: Pull off the front
Now gently pull of the front
Step 6: The belts
These are the two belts we want to replace
Step 7: Unscrew the 2 tiny screws
Unscrew the 2 tiny screws on the deck on which you like to replace the belts
Step 8: Final Step
Now remove the top part of the deck, replace the belts and then reassemble.