Is it permissible for the buyer to claim compensation for damages resulting from the seller's failure to repair the machine or to demand its return, after having purchased the machine based on the availability of its spare parts, and then it became clear that the seller was unable to repair it due to the unavailability of those parts?

The sale is valid and enforceable, and the buyer has no right to return the machine except with the seller's consent, as the seller is neither deceptive nor fraudulent. Similarly, the buyer has no right to claim rent for the machine during its downtime, nor is the seller obliged to travel to acquire spare parts. Blame and liability might be directed at the seller if he was an agent or partner and was negligent, and this would be decided by experts or the Sharia judiciary.