I am currently on a break from the business, so I do not know how the current bankruptcy is affecting parts.
I know the Chrysler bankruptcy in the 70's caused lots of parts issues. The quality went down, and the prices went way up.
The OEM parts warehouses always close for about 10 days, the last week of the year, and the beginning of the new year. So right before Christmas, is always the worst time to get in a big wreck, if your in a hurry to get your car back.
As far as other times, who knows why they run out of certain parts. I am sure modern "just in time" inventories are a big factor.
When I order a new door for a Dodge truck like this, it is not uncommon for it to arrive damaged. They are big and heavy, and poorly packaged. A very bad combination. This almost always causes lost production time.
When Chrysler first made the LHS, I had a customer with one that was almost brand new. He got rear ended, and needed a new deck lid, (trunk).
Chrysler was selling them faster than they could build them, so they were putting all the parts into production, and few were available for crash parts.
After one month, a deck lid arrived,...and it was damaged. We reordered it,....3 weeks later it came,...damaged. We reordered it 3 weeks later it came,..it was also damaged. The boxes were not damaged, scuffed, or marked, but each one had a big dent right in the middle. It did not take a rocket scientist to see they were shipping us the rejects they could not use at the factory. Minor damage on new parts is not uncommon, but this was not minor damage. At this point, the disgusted customer approved repairing the damaged, brand new deck lid, being we were now 10 weeks into the job, and unable to even start the repairs.
A week later, it was done. And, all the guys neighbors and friends knew was, it took my shop 11 weeks to put a deck lid, and a bumper on the car.