Lose hardware wallet device - your safe as long as you have seed right?
Hardware device breaks- ditto
Forget PIN- ditto
You can recover with the seed phrase, this should not be a problem usually.
Some users use various wallet software, each behaving different and they may end up, for example, with the coins at a derivation path unexpected by the next software (legacy vs SegWit, use of sub-accounts..), but with a bit of help, this can be recovered easily.
Lose seed words- you can still transfer your coins to a different wallet with new seed words right?
In theory yes, in reality, most notice they've lost their seed when they already lost access to the wallet and want to recover. And then it's too late.
How do people get in trouble with self cold storage?
Your questions are about hardware wallets actually, hence that's what I'll answer about:
* One case is, as said, lost seed and lost access to the wallet.
* Another case is saving the seed "safely" somewhere online (hint: that's the opposite of keeping safe), like email or cloud.
* Some do tests and end up receiving coins in a wallet actually not related to the addresses generated by the hardware wallet.
* Some use fake wallet and that could maybe replace recipient address (but one has to be careless when signing the tx with the hardware wallet)
* Some have the computer infected and for example the malware watches the system clipboard and replaces the recipient address with the hacker's address, hence the user sends transactions to the hacker's address instead of wherever it was intended to (but again one has to be careless when signing the tx with the hardware wallet); of course, this same can happen when withdrawing from exchange to own wallet and then the exchange will send the funds to wrong address and there's no double check on hardware wallet screen.