I hope you get it resolved one way or another,problems like this make me feel physically sick when they happen,when you know you packed and sent it in good order.
What makes me mad about the necessity for courier (or postage) insurance is that basically the company are saying “we can’t trust ourselves to deliver your item intact.”
Gust a thought, what happens if it gets damaged on its return leg????
I’ve had the same issue with some computer parts, they got returned as a pin had got bent in transit (only 1), whe I got it back it was completely buggered.
You should check the TNCs for couriers when shipping bikes. Most won’t cover frame damage, but will happily let you pay for additional compensation for loss only.
Sorry to hear you’ve had so many issues, sure it’s really frustrating…for this reason I only trade online for PayPal gift payments for cheaper items or cash on collection for anything over £50ish.