My wife's uncle gave me an ice machine/maker that he doesn't use anymore.

He said the machine works and makes ice, but it has one issue. Once the ice was made and in the bin, it had a hard time staying frozen and it would slowly start to melt. He assumed that it might have been because the machine sat in a warm/sunny spot of his house.

I plan on putting the machine in the building where I do all my canning and processing and it does get warm in the summer.

Does it sound like the machine has a problem that can be fixed? What should I do?

If the machine you have is like one my son has. It's not made to store ice only make it fairly quick. He runs little one he has while he is home and can dump the tray in tub in freezer. One his freinds also has one sits on back bar in his basement that runs when they watch football or campfire in yard.
So anyways my guess is that is kinda unit you have. Made for someplace don't have ice maker in fridge freezer
My son takes his to the camper.

Mac

This is a fairly large machine. More commercial size. Not one of the counter top models.

Is there a Bin Thermistor where the cubes are stored?

You can talk to a restaurant owner or manager. And see who they use to maintain their ice machine. I would fix it.

Most that i was familiar with were holding bins only, the bin is most likely insulated and the constant replenishment of ice keeps the bin full, there is a "thermostat" thingee that shuts the ice making process down when the ice reaches a certain level. Warm temps, direct sun, hot kitchen will determine how fast the ice melts, the insulation of the bin may be soaked and not doing it's job also.

Commercial ice machine with bin aren't meant to hold ice for long before the ice starts to melt and the ice becomes a big block of ice. The bin has no refrigeration in it. The ice has to be used daily. Sounds like there's nothing wrong with the ice machine.

Sounds like it working correctly.
The ones we install either have a pump for the melting ice or we core drill a drain through the concrete slab and gravity drain it to a wet stack in the building.

For the pump we add an open drain, like a funnel and tie it into the sink waste.

Everyone who's posted before is correct. The ice maker is the top part. The bottom part is just an insulated storage bin. The storage bin doesn't have any cooling to keep the ice cold. In a restaurant or bar, you are using ice from the bin as quickly as the top section is refilling the bin - no real storage of ice.

If you want to store ice, you'll need to bag it and put it in a freezer.

OR, you can mount it on a modified small freezer if you need large quantity's.

I agree. The ice must be bagged to freeze or if dropped into a freezer it will freeze into a big lump. The reason is that the ice is or can be slightly wet when it comes out of the maker. It gets wetter as it sits in the tub and begins to slowly thaw. Best for continuous us as stated above.

And there you go, complete understanding in short order.

I have a comercial ice machine in my shop.scottsman prodigy with 1,000 pund bin.yes these fellas are correct the bin does not freeze the ice.also have an ice bagger and a chest freezer that my daughter keeps stocked up.she sells the bagged ice for 2$ a bag to our friends and neighbors.she is only 9 and gets some looks at the store when she pulls out 20$ bills at the store to buy candy lol.the drain for my ice bin is ran out through the wall to my dogs water bowel with is a small blue plastic kiddie pool.i often joke with friends and tell them my dogs are so spoiled they will only drink cold filtered ice water lol