I had both problems mentioned here on a trip last week and was not a happy camper. On the outbound it didn't give me the PreCheck on the boarding pass and I didn't notice until getting in the PreCheck line. Even though in ATL they only need driver's licenses it still wouldn't work. I got an unusually very helpful TSA person who walked me to the front of the regular line (major kudos to him), which likely made the difference between catching and missing the flight. Very irritated at Frontier for the unexpected problem, though.

On the way back (and a different locator number, as I'd booked it as two one-ways) the PreCheck appeared, but I was within the 24-hour window and even when logged into my account it wasn't doing the seating options properly, treating me as a regular customer (not a Gold elite) and wanting to charge not only for stretch seats or exit row, but to switch to any other seat. So I didn't go through with it and kept trying again until it finally worked as it should with about 10 hours to go. But since it was a trans-con there wasn't too much to choose from by the time it worked. Though I did notice that the seats I was trying to get stayed unclaimed for the first few tries, so maybe the problem was affecting everyone. Not that that's much consolation.

They definitely need to get both problems fixed, though.

The outbound one-way was a paid ticket and the return an award ticket. Still no miles at all posted for the paid ticket 6 days later. Though that's minor compared to the other problems.

The return was a connecting flight that was late and wouldn't have connected, and they were able to catch it on time to put me on a non-stop instead (resulting in a concourse-to-concourse dash). So at least that part worked.