Wwise 2019.2.5 in legacy mode has problems with events - converted sounds won't play in editor

Question

we have hundreds of banks and thousands of sounds (with thousands of references) in our project that used to use 2019.1.7  and UE 4.24.  We can't convert to event-based packaging because of the amount of data it impacts.  I find that running generate-banks on an existing bank won't work.  All sounds give me a "Event ID not found" error.  If I create a new bank, use "Group into sound bank" and generate that bank, then those sounds will play.  However -- if after that, I "group into sound bank" to put them back into the sound bank that I really want to use, and generate banks, it still seems to play.  If I close & reopen the editor, I can use Epic's reference editor to confirm that the AkAudioEvents are now back to the bank I want, and their "required banks" refers to the bank I want.  However, if I delete the theoretically unused new bank, the event IDs can't be found again.

This implies to me that I can't get the existing banks to register the events, and that the "unused" bank (unused according to Epic's tools) still needs to be in the data in order to find the event IDs.

 

Has anyone else seen this -- or does anyone have a work-around?