Ok, I get that screen (black, blank - Hung-up) screen when I bring my phone along and FORGET to turn off the phones Bluetooth and ensure the Syncs' own BT isn't trying to "sync" with it. (Looking for an App)
So was curious - else are you getting really hot days? Some electronics shut down, not due to "electrical fault" but their own in-operation heat they generate as well as are operated in, the car interior - gets pretty warm. Many audio amp modules in todays radios have thermal shut-down built into them, and will shut down themselves - leaving you with what appears as a "Dead radio" because the part used in the Audio Amp - the amplifier module itself - feels the heat building from being operated, on top of, the fact that - the outside temp - can be too much heat and shuts down - they don't make them like they used to.
- If you use a CD player, you also needed to remember to "eject" the disc before you parked the car on hot sunny days, else you'd lose it (CD) and possibly damage the radio from the warping the CD could do in the heat.
The construction of the Sync DIN radio is not like other aftermarkets that seem to have more experience and know-how to understand that people will crank up radios and have moments of
I gotta hear that again - you may not have those tendencies, but someday you may be waiting at a light to change and the guy pulls up next to you blaring out their music for the entire city block to hear.
Other efforts; like knowing the IMPEDANCE load the speaker presents itself as to the Audio amp. The right measure of resistive loading to match the expected load the module is designed to load into - can go a long way in making the radio live a lot longer. Some of the Fiesta's have 6 speakers. Two pairs are "tied" in parallel - front and single in rear, presents an impedance load of 2~3 ohms instead of 4~8 ohms - makes it pull a lot more current thru the amp so it can push its' music to the speakers for you to enjoy the moment.
Before,
(its' been a decade but seems a lot shorter than that) the radio had a big heat sink and thicker metal panels to hold itself to the DIN cubby - offered a way to transfer heat away. Mine did something similar to yours - so the first time - the last time, I looked at my unit - it doesn't have the external fins. It's a square rectangle "box". Metal yes,- it's about the same "gauge" as the tin cap off of a Dinty Moore Stew. it may have those modules bolted internal mounting to transfer heat away, but that does you no good when it's never transferred to the outside.
Look at the dashboard - little ventilation - Can't equalize, or find thermal equilibrium from inside to outside. The problems isn't just the heat the parts produce - it's not just the case and what's' inside it - the case sits in the heat too. Thin materials may take up heat faster - but they can't dissipate the heat when the heaters on or the outside temp is nearing the 35~38 C outside. Not without ventilation. Metals' heat transfer works both ways - and transfers in the heat from outside to the parts inside - while you are driving, same in Summer as in the Winter - does the same effects and results.
Some vehicles ventilation used to "leak air" behind the dash to help reduce the dashboard console and speedo/odo/gauge cluster to help reduce fogging.
They just want to save weight - less mass, more inertia...
There's another thread of a similar situation - may be more electrical glitches but still something you can read thru and possibly help you out.
https://www.fordfiesta.org/threads/think-my-radio-bit-the-dust.7979/post-18614