Inexplicable internal damage to USB-C ports: cause?

Apple diagnoses internal damage to pins on 2 of the 4 ports on high-spec MacBook Pro. It’s being classed as 'accidental damage’ with a £79 excess to repair. Given that Mac is less than two years old and has had only one careful, experienced user (me), I'm struggling to understand how 'accidental damage’ - to opposite sides of the device no less - is possible.*

I believe this is a failure of hardware that's been exposed to perfectly normal usage. Any laptop should be able to withstand the normal plugging / unplugging of external devices for several years, let alone 18 months - and having worked in tech I suspect I’m considerably more careful with my gear than the average user.

The problem crept up slowly. I didn’t connect the dots and blamed other devices, but on reviewing screen grabs and notes a different picture emerges:

• ± 18 months ago: one external monitor randomly goes black, displaying 'no signal' messages. I replace it.
• ± 12 months ago: Mac occasionally overheats, but still much cooler than previous models.
• ± 6 months ago: Mac overheats more frequently. It also occasionally tips external hard drives off, resulting in error messages saying to eject discs before removing - but disks haven't been touched. (And if I unplug them of course I eject first. Duh). Place new fan beneath Mac.
• Disk eject problem continues. Suspect old HDD and change it.
• ± 4 months ago. Another (new) new hard disk operates well below described speed; I return it.
• ‘Disk eject’ occurrences escalate further; one drive corrupts, fatally. Data irretrievable and disk can't be re-formatted. Fried.
• Another external monitor starts to go black and display 'no signal’ message. Usual steps – power on off, reboot etc. fails to resolve it. Fault on (very expensive) 1 year old monitor??
• ± 6 weeks ago, second screen (only 8 weeks old) starts doing the same thing...
• Disk ejection error messages escalate, although disks always untouched. Mac overheats more often, and hotter. Mac occasionally unresponsive, screen lag, apps not responding in real time. Random problems with slow data transfer. Error message saying current Thunderbolt port only able to transfer data at ridiculously slow speed. (Forget what but something like 0.04 mbps). So, H/W fault. Add Thunderbolt 4 hub (own power supply) to enable other HDDs to continue without using that port. Disk eject problem continues. Mac overheats even when not using demanding apps.

With the diagnoses of inexplicably damaged pins on 2/4 ports I finally realise problems with peripherals are consistent with frequent, intermittent and uncontrolled disconnection of external devices. Whilst evaluating computer, Apple advisor experienced screen freeze and Mac inexplicably getting much too hot, although no applications actually in use. I was then advised that if found further evidence of damage found inside – such as liquid damage - the repair could cost more.

The Mac has never been exposed to liquid, used in extreme temperatures or wet atmosphere. No kids in the house, never been dropped, gets transported with care in own compartment of laptop rucksack. Has never had anything other than USB-C cables and an Apple multiport adapter (carefully) plugged into its ports. Except for one SSD, all external devices have own power supply. External monitors x 2 are well within performance spec for this model.

I’d be grateful for input from any hardware techs. I think it's shoddy hardware, not 'accidental damage’ and I'm very unhappy at being charged an excess and discovering that this counts as one of only two accidental damage incidents allowable under the ludicrously expensive AppleCare policy.