The short answer is that the safe harbor defined in IRS Rev. Proc. 2019-13 expired when 100% bonus depreciation ended.  There's a KPMG article confirming this.  "The safe harbor method does not apply to a passenger automobile placed in service by the taxpayer after 2022"

So in 2023 with an 80% bonus depreciation you remove 80% of the basis of the asset to give to Section 168(k), that leaves 20% of the asset left to go through regular depreciation.  Under the "normal" rules the excess over the Section 280F limits only comes back after we fall off of the 6-year MACRS table.  RP-19-13 was extremely taxpayer friendly for as long as 100% bonus depreciation applied.  But now we're back to the law of unintended consequences.

My math looks something like this:

Is that what you're seeing in Lacerte 2024?  My guess is the programmers didn't look beyond 12/31/23 for the 2023 software, then they had to correct it for 2024.

Rick